From Wikipedia, the free encyclopedia

Tivoization is the creation of a system that incorporates software under the terms of a copyleft software license, but uses hardware 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.^[1]. The term came about in reference to TiVo's use of GNU GPL licensed software on the TiVo brand digital video recorders (DVR).

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'd software to modify the software to better suit their purposes.^[2]

However, Stallman believes TiVo circumvented this goal by making their products run programs only if the program's digital signature matches those authorised by the manufacturer of the TiVo.^[3] 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 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 are a beneficial security tool. Torvalds also believes that software licenses should attempt to control only software, not the hardware on which it runs. So 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.^[4] Other Linux developers, including Alan Cox,^[5] 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.

As a result, one of the goals of the proposed 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."^[6]

Draft 2 of GPLv3 attempted to clarify this.^[7] However, many Linux developers were still concerned that draft 2 GPLv3 may still prohibit beneficial uses of digital signatures.^[8]

In the third and fourth discussion drafts of GPLv3, released March 28, 2007 and May 31, 2007 respectively, the anti-tivoisation clause was limited so as not to apply when the software is distributed to a business.^[9] Thus, medical devices and voting machines would not be covered. Linus Torvalds has said he is "pretty pleased" with the new draft and its stance on DRM.^[10] The final, official GPLv3 was published on June 29, 2007 with no major changes in respect to tivoization relative to the fourth draft.

• 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 kernel, 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 Moglen's explanations:
  • Spain, June 2006
• Ciaran O'Riordan's explanations:
  • Japan, November 2006
  • Tivoisation explained - implementation and harms (article)
• "Using a hypervisor to reconcile GPL and proprietary embedded code" article with a focus on Tivoization