To understand why FSF thinks of DRM as restricting users' freedom, one needs to understand the meaning of copyleft and the essence of the GPL. This license upheld the four provisions of copyleft:
(a) the freedom to use the software,
(b) the freedom to copy and share the software,
(c) the freedom to modify the software (this requires the source code to be available), and
(d) the freedom to run and distribute modified software.
The use of DRM to disallow freedoms (c) and (d) is what FSF doesn't like. Richard Stallman (RMS), founder of the FSF, calls this situation Tivoization. The term originates from TiVo, a digital video recording device that allows users to record television programs to an internal hard disk for later viewing. Tivo runs on Linux-based software, which means that it is governed by the GPL. That is, the source code is available, the users have the right to modify the source code, and they have the right to run the modified source code.
But with TiVo this doesn't happen.
While one can modify the source code of TiVo's Linux-based software, one can't run it. The product's DRM enforcement prevents users from running modified versions of the code on their systems. This conflicts with the freedoms and provisions of the GPL. The DRM in this regard acts as a restriction; users are restricted from exercising the right to run the modified source code.
The makers of TiVo include a digital key into the software, somewhat similar to the md5sum value that people can check after they download software. Users can compare the md5sum of the download against the md5sum value listed on the site from which the software came in order to make sure they are getting the complete, genuine thing.
In the case of TiVo, the digital key makes sure that the software was written by the makers of TiVo. If you change the source code and recompile it, the digital keys will no longer match, and when the system sees that, it will prevent you from running the modified software.
Tivoization doesn't apply just to TiVo, but to all instances of DRM usage that restrict the freedoms offered to the users by GPL.
GPLv3 explicitly asks software makers to provide whatever digital keys they use such that people who wish to run modified versions of the software can do so by using this key on their modified version. At the 3rd international conference on GPLv3, held in Barcelona in June, RMS said, "They can design the hardware so that it requires the binaries to be signed by a certain signature key in order to run, but they must give you the signature key so that you can sign your modified binaries. They must give you whatever it takes to authorize your version so that it will run."
But Linus Torvalds, the creator of Linux, has a problem with this. He says that he himself signs the Linux kernel, and that that's his way of telling everyone, "You can trust this, it's from me." In an email message to the Linux Kernel Mailing List (LKML) on 23 April, he says that there are two types of keys: "One is an external key that is applied _to_ the kernel (OK, and outside the license), and the other one is embedding a key _into_ the kernel."
GPLv3 says that if any GPLed software carries an embedded key, this key should me made available to the users, but it makes no demands on the first kind of key. Linus has said that he would never distribute his signing keys, but the GPLv3 does not require him to release them. The key he talks about only describe the trustworthiness of the kernel. It in no way affects the freedoms of copyleft. It's only the embedded keys, which can be used to nullify the freedoms offered by copyleft, that need to be released.
Linus has repeatedly claimed that it is not for a license to decide how a manufacturer uses digital keys. He says the key are firmware, and therefore a software license has no scope or reason for controlling this.
Eben Moglen addressed that concern during the conference in Barcelona. Moglen, general counsel of the Free Software Foundation and chairman of Software Freedom Law Center, said, "You will hear a lot of talk about DRM in which it is suggested that we are somehow trying to use a software licence to address non-software issues. Nothing could be further from the truth; we are addressing a software issue.... And by the way, what you are not allowed to do by illegally modifying the licence, you are not allowed to do by modifying the hardware so that the licence can be evaded safely. It's a straightforward proposition: you can't do it this way and you can't do it that way either."
GPLv3 not alone
Contrary to common belief, GPLv3 is not the first license to denounce DRM. Against DRM 2.0 is a free copyleft license for art works; it cannot be used for software. Section 6 of this license states:
This license is incompatible with any technology, device or component that, in the normal course of its operation, is designed to prevent or restrict acts which are authorised or not authorised by licensor: this incompatibility causes the inapplicability of the license to the work.In particular:
a. it is not possible to release validly under this license works or derivative works whose access control mechanism and/or copy control mechanism prevents or restricts quantitatively and/or qualitatively access to, fruition, copy, modification and/or sharing of them;
b. in conformity with this license, it is not allowed to prevent or restrict quantitatively and/or qualitatively access to, fruition, copy, modification, and/or sharing of works or derivative works through an access control mechanism and/or a copy control mechanism;
c. in conformity with this license, it is not allowed to prevent or restrict the exercise of a granted right through any digital, analog or physical method.
Even the Creative Common Attribution-ShareAlike license includes an anti-DRM clause. Section 4.a states:
You may not distribute, publicly display, publicly perform, or publicly digitally perform the Work with any technological measures that control access or use of the Work in a manner inconsistent with the terms of this License Agreement.
"Technological measures" refer to DRM. The second draft of GPLv3 has similar wording. Section 3 is titled "No Denying Users' Rights through Technical Measures."
The FSF and Stallman have explained many times that they believe there is nothing wrong with DRM itself; they only wish to protect the freedoms and provisions offered by the GPL. As long as the use of DRM does not hinder the four freedoms of copyleft, it's fine. GPLv3 takes steps to clarifying that.
Moglen recently said, "If you're keeping the right to modify and not conveying that right to modify, you're violating the licence." The FSF says, "GPLv3 does not prohibit the implementation of DRM features, but prevents them from being imposed on users in a way that they cannot remove." Moglen further added that it'd be fine for manufacturers to nullify warranty and not provide support if modified software is used.
The 4th international conference, to be held in Bangalore, India on 23-24 August will have extensive discussions on DRM.
Shashank Sharma is studying for a degree in computer science. He specializes in writing about free and open source software for new users.