Tivoization

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Tivoization /ˈtvɨˌzʃən/ is 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 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.[1][2] Stallman believes this practice denies users some of the freedom that the GNU General Public License (GNU GPL) was designed to protect.[3]

Overview[edit]

TiVo's software incorporates the Linux kernel 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-covered software to modify the software to better suit their purposes.[4]

However, Stallman asserts that 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.[5] 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.

Linus Torvalds, the original author of the Linux kernel, has said that he personally doesn't like DRM, but on the other hand, argued that it is appropriate for TiVo to decide if they will 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.[6] Other Linux developers, including Alan Cox, have expressed divergent opinions.[7]

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[edit]

In 2006, Free Software Foundation (FSF) decided to combat TiVo's technical system of blocking users from running modified software. As the FSF was developing a new version of the GNU General Public License (GPL v3), it included language that prohibited this activity.[8] 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".[9] Regardless, the Linux kernel has not been changed to use GPL v3.

GPLv3[edit]

One of the goals of GPL Version 3 is to prevent "Tivoization". According to Eben Moglen, "the licence should prohibit technical means of evasion of its rules, with the same clarity that it prohibits legal evasion of its rules."[10]

Draft 2 of GPLv3 attempted to clarify this.[11] However, some Linux kernel developers were still concerned that draft 2 GPLv3 may still prohibit beneficial uses of digital signatures.[12]

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.[13] 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.[14] However, he still does not support relicensing the Linux kernel under GPLv3, stating that:[15]

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.[16]

Some other projects widely used in Tivoized embedded systems, such as BusyBox, have also declined to move to GPLv3.[17]

See also[edit]

References[edit]

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