Tivoization
Encyclopedia
Tivoization is a coined term to describe the creation of a system that incorporates software under the terms of a copyleft
software license (like the GPL), but uses hardware restrictions
to prevent users from running modified versions of the software on that hardware. Richard Stallman
coined the term and believes this practice denies users some of the freedom that the GNU General Public License
(GNU GPL) was designed to protect. The term came about in reference to TiVo
's use of GNU GPL licensed software on the TiVo brand digital video recorders (DVR)
which actively blocks users from running modified software on its hardware by design.
and GNU
software, both of which are licensed under version 2 of the GNU General Public License
(GPLv2). GPLv2 requires distributors to make the corresponding source code
available to each person who receives the software. The goal of this requirement is to allow users of GPL'd software to modify the software to better suit their purposes.
However, Stallman believes TiVo circumvented this goal by making their products run programs only if the program's digital signature
matches those authorized by the manufacturer of the TiVo. So while TiVo has complied with the GPL v2 requirement to release the source code for others to modify, any modified software will not run on TiVo's hardware.
On the other hand, Linus Torvalds
, the original author of the Linux kernel, has argued that it is appropriate for TiVo to use digital signatures to limit what software may run on the systems that they sell. Torvalds has stated that he believes the use of private digital signatures on software is a beneficial security tool. Torvalds also believes that software licenses should attempt to control only software, not the hardware on which it runs. So, as long as one has access to the software, and can modify it to run on some other hardware, Torvalds believes there is nothing unethical about using digital signatures to prevent running modified copies of Linux. Other Linux developers, including Alan Cox
, have expressed divergent opinions.
Stallman and the Free Software Foundation have attempted to respond to some of these concerns. They have stated that their goal is for GPLv3 to allow private digital signatures for security purposes, but to still prevent Tivoization.
(FSF) decided to combat TiVo's technical system of blocking users from running modified software. The practice was tackled by creating a new version of the GNU General Public License (GPL v3) prohibiting this activity. The operating system kernel included in the TiVo is distributed under the terms of the GPL, and the FSF's goal is to ensure that all recipients of software licensed under the new GPL are not restricted by hardware constraints on the modification of distributed software. This new license provision was acknowledged by TiVo in its April 2007 SEC filing
: "we may be unable to incorporate future enhancements to the GNU/Linux operating system into our software, which could adversely affect our business". Regardless, the Linux kernel has not been changed to use GPL v3.
, "the licence should prohibit technical means of evasion of its rules, with the same clarity that it prohibits legal evasion of its rules."
Draft 2 of GPLv3 attempted to clarify this. However, some Linux kernel developers were still concerned that draft 2 GPLv3 may still prohibit beneficial uses of digital signatures.
In the third and fourth discussion drafts of GPLv3, released March 28, 2007 and May 31, 2007 respectively, the anti-tivoization clause was limited so as not to apply when the software is distributed to a business. Thus, medical devices and voting machines would not be covered. The final, official GPLv3 was published on June 29, 2007 with no major changes in respect to tivoization relative to the fourth draft.
Linus Torvalds
said he was "pretty pleased" with the new draft's stance on DRM
. However, he still does not support relicensing the Linux kernel under GPLv3:
In any case, changing the license of the Linux kernel would likely be infeasible due to its very large number of copyright holders. Unlike most GPL software, the kernel is licensed only under GPLv2 without the wording "or, at
your option, any later version", therefore the agreement of all copyright holders would be required to relicense under a new version.
Some other projects widely used in Tivoized embedded systems, such as Busybox
, have also declined to move to GPLv3.
Copyleft
Copyleft is a play on the word copyright to describe the practice of using copyright law to offer the right to distribute copies and modified versions of a work and requiring that the same rights be preserved in modified versions of the work...
software license (like the GPL), but uses hardware restrictions
Hardware restrictions
Hardware restrictions refers to restrictions in any device that places technical restrictions on what content can run/play on said device or what users can do with certain content. Hardware restrictions can be used with software DRM and digital signatures...
to prevent users from running modified versions of the software on that hardware. Richard Stallman
Richard Stallman
Richard Matthew Stallman , often shortened to rms,"'Richard Stallman' is just my mundane name; you can call me 'rms'"|last= Stallman|first= Richard|date= N.D.|work=Richard Stallman's homepage...
coined the term and believes this practice denies users some of the freedom that the GNU General Public License
GNU General Public License
The GNU General Public License is the most widely used free software license, originally written by Richard Stallman for the GNU Project....
(GNU GPL) was designed to protect. The term came about in reference to TiVo
TiVo
TiVo is a digital video recorder developed and marketed by TiVo, Inc. and introduced in 1999. TiVo provides an on-screen guide of scheduled broadcast programming television programs, whose features include "Season Pass" schedules which record every new episode of a series, and "WishList"...
's use of GNU GPL licensed software on the TiVo brand digital video recorders (DVR)
Digital video recorder
A digital video recorder , sometimes referred to by the merchandising term personal video recorder , is a consumer electronics device or application software that records video in a digital format to a disk drive, USB flash drive, SD memory card or other local or networked mass storage device...
which actively blocks users from running modified software on its hardware by design.
Overview
TiVo's software incorporates the Linux kernelLinux kernel
The Linux kernel is an operating system kernel used by the Linux family of Unix-like operating systems. It is one of the most prominent examples of free and open source software....
and GNU
GNU
GNU is a Unix-like computer operating system developed by the GNU project, ultimately aiming to be a "complete Unix-compatible software system"...
software, both of which are licensed under version 2 of the GNU General Public License
GNU General Public License
The GNU General Public License is the most widely used free software license, originally written by Richard Stallman for the GNU Project....
(GPLv2). GPLv2 requires distributors to make the corresponding source code
Source code
In computer science, source code is text written using the format and syntax of the programming language that it is being written in. Such a language is specially designed to facilitate the work of computer programmers, who specify the actions to be performed by a computer mostly by writing source...
available to each person who receives the software. The goal of this requirement is to allow users of GPL'd software to modify the software to better suit their purposes.
However, Stallman believes TiVo circumvented this goal by making their products run programs only if the program's digital signature
Digital signature
A digital signature or digital signature scheme is a mathematical scheme for demonstrating the authenticity of a digital message or document. A valid digital signature gives a recipient reason to believe that the message was created by a known sender, and that it was not altered in transit...
matches those authorized by the manufacturer of the TiVo. So while TiVo has complied with the GPL v2 requirement to release the source code for others to modify, any modified software will not run on TiVo's hardware.
On the other hand, Linus Torvalds
Linus Torvalds
Linus Benedict Torvalds is a Finnish software engineer and hacker, best known for having initiated the development of the open source Linux kernel. He later became the chief architect of the Linux kernel, and now acts as the project's coordinator...
, the original author of the Linux kernel, has argued that it is appropriate for TiVo to use digital signatures to limit what software may run on the systems that they sell. Torvalds has stated that he believes the use of private digital signatures on software is a beneficial security tool. Torvalds also believes that software licenses should attempt to control only software, not the hardware on which it runs. So, as long as one has access to the software, and can modify it to run on some other hardware, Torvalds believes there is nothing unethical about using digital signatures to prevent running modified copies of Linux. Other Linux developers, including Alan Cox
Alan Cox
Alan Cox is a British computer programmer who formerly maintained the 2.2 branch of the Linux kernel and continues to be heavily involved in the development of the Linux kernel, an association that dates back to 1991...
, have expressed divergent opinions.
Stallman and the Free Software Foundation have attempted to respond to some of these concerns. They have stated that their goal is for GPLv3 to allow private digital signatures for security purposes, but to still prevent Tivoization.
Response
In 2006, Free Software FoundationFree Software Foundation
The Free Software Foundation is a non-profit corporation founded by Richard Stallman on 4 October 1985 to support the free software movement, a copyleft-based movement which aims to promote the universal freedom to create, distribute and modify computer software...
(FSF) decided to combat TiVo's technical system of blocking users from running modified software. The practice was tackled by creating a new version of the GNU General Public License (GPL v3) prohibiting this activity. The operating system kernel included in the TiVo is distributed under the terms of the GPL, and the FSF's goal is to ensure that all recipients of software licensed under the new GPL are not restricted by hardware constraints on the modification of distributed software. This new license provision was acknowledged by TiVo in its April 2007 SEC filing
SEC filing
An SEC filing is a financial statement or other formal document submitted to the U.S. Securities and Exchange Commission . Public companies, certain insiders, and broker-dealers are required to make regular SEC filings. Investors and financial professionals rely on these filings for information...
: "we may be unable to incorporate future enhancements to the GNU/Linux operating system into our software, which could adversely affect our business". Regardless, the Linux kernel has not been changed to use GPL v3.
GPLv3
One of the goals of GPL Version 3 is to prevent "Tivoization". According to Eben MoglenEben Moglen
Eben Moglen is a professor of law and legal history at Columbia University, and is the founder, Director-Counsel and Chairman of Software Freedom Law Center, whose client list includes numerous pro bono clients, such as the Free Software Foundation....
, "the licence should prohibit technical means of evasion of its rules, with the same clarity that it prohibits legal evasion of its rules."
Draft 2 of GPLv3 attempted to clarify this. However, some Linux kernel developers were still concerned that draft 2 GPLv3 may still prohibit beneficial uses of digital signatures.
In the third and fourth discussion drafts of GPLv3, released March 28, 2007 and May 31, 2007 respectively, the anti-tivoization clause was limited so as not to apply when the software is distributed to a business. Thus, medical devices and voting machines would not be covered. The final, official GPLv3 was published on June 29, 2007 with no major changes in respect to tivoization relative to the fourth draft.
Linus Torvalds
Linus Torvalds
Linus Benedict Torvalds is a Finnish software engineer and hacker, best known for having initiated the development of the open source Linux kernel. He later became the chief architect of the Linux kernel, and now acts as the project's coordinator...
said he was "pretty pleased" with the new draft's stance on DRM
Digital rights management
Digital rights management is a class of access control technologies that are used by hardware manufacturers, publishers, copyright holders and individuals with the intent to limit the use of digital content and devices after sale. DRM is any technology that inhibits uses of digital content that...
. However, he still does not support relicensing the Linux kernel under GPLv3:
In any case, changing the license of the Linux kernel would likely be infeasible due to its very large number of copyright holders. Unlike most GPL software, the kernel is licensed only under GPLv2 without the wording "or, at
your option, any later version", therefore the agreement of all copyright holders would be required to relicense under a new version.
Some other projects widely used in Tivoized embedded systems, such as Busybox
BusyBox
BusyBox provides several stripped-down Unix tools in a single executable. It runs in a variety of POSIX environments such as Linux, Android, FreeBSD and others, such as proprietary kernels, although many of the tools it provides are designed to work with interfaces provided by the Linux kernel. It...
, have also declined to move to GPLv3.
See also
- TiVoTiVoTiVo is a digital video recorder developed and marketed by TiVo, Inc. and introduced in 1999. TiVo provides an on-screen guide of scheduled broadcast programming television programs, whose features include "Season Pass" schedules which record every new episode of a series, and "WishList"...
- GPL (GNU General Public License)GNU General Public LicenseThe GNU General Public License is the most widely used free software license, originally written by Richard Stallman for the GNU Project....
- Free Software FoundationFree Software FoundationThe Free Software Foundation is a non-profit corporation founded by Richard Stallman on 4 October 1985 to support the free software movement, a copyleft-based movement which aims to promote the universal freedom to create, distribute and modify computer software...
- Vendor lock-inVendor lock-inIn economics, vendor lock-in, also known as proprietary lock-in or customer lock-in, makes a customer dependent on a vendor for products and services, unable to use another vendor without substantial switching costs...
External links
- Free Software Foundation definition of "Tivoization"
- An Introduction to Tivoization by The Linux Information Project (LINFO)
- Stallman, Torvalds, Moglen share views on DRM and GPLv3 - by Shashank Sharma August 09, 2006, from Newsforge
- TiVo's GPL-required modifications to the Linux kernelLinux kernelThe Linux kernel is an operating system kernel used by the Linux family of Unix-like operating systems. It is one of the most prominent examples of free and open source software....
, glibc, and other software - Richard Stallman's explanations of "tivoisation":
- Italy, March 2006
- Brazil, April 2006
- Spain, June 2006
- India, August 2006
- Japan, November 2006
- Stallman and Bruce Perens debating about GPL and tivoization (on Wikimedia Commons)
- Eben MoglenEben MoglenEben Moglen is a professor of law and legal history at Columbia University, and is the founder, Director-Counsel and Chairman of Software Freedom Law Center, whose client list includes numerous pro bono clients, such as the Free Software Foundation....
's explanations: - Ciarán O'Riordan's explanations:
- "Using a hypervisor to reconcile GPL and proprietary embedded code" article with a focus on Tivoization