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Richard Stallman said that version 3 of the GNU General License (GPLv3) will prevent 'tivoization', restrict DRM and protect software developers from patent litigation, particularly litigation by Microsoft.

Tivoization - named after set-top box maker TiVo, refers to computers and devices that contain open-source software covered by GPL that you cannot change, because the appliance shuts down if it detects modified software.

TiVo boxes are designed to shut down if the software is hacked by users trying to circumvent DRM features, for example. In a recent regulatory filing the company warned investors that if GPLv3 is widely adopted, 'we may be unable to incorporate future enhancements to the GNU/Linux operating system into our software, which could adversely affect our business'.

Stallman argues that free software works both ways. 'The manufacturers of these computers take advantage of the freedom that free software provides, but they don't let you do likewise,' Stallman says. 'Freedom means you control what your software does, not merely that you can beg or threaten someone else who decides for you.'

Turning to DRM, he notes that GPLv3 does not prohibit copy protection, but instead permits users of DRM-restricted software to remove the restrictions. 'GPLv3 ensures you are free to remove the handcuffs,' he says. 'It doesn't forbid DRM, or any kind of feature. It places no limits on the substantive functionality you can add to a program, or remove from it. Rather, it makes sure that you are just as free to remove nasty features as the distributor of your copy was to add them.'

GPLv3 will also protect free software developers from litigation by Microsoft, which recently signed an agreement with Novell in which it promised not to sue Novell customers for violating patents that it claims are breached by the open-source Linux operating system.

Microsoft clause

Following that deal, the Free Software Foundation tweaked the GPLv3 draft to counter the implied Microsoft threat. 'Microsoft wants to use its thousands of patents to make GNU/Linux users pay Microsoft for the privilege, and made this deal to try to get that. The deal offers Novell's customers rather limited protection from Microsoft patents,' Stallman

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explains.

'Microsoft made a few mistakes in the Novell-Microsoft deal, and GPLv3 is designed to turn them against Microsoft, extending that limited patent protection to the whole community. In order to take advantage of this, programs need to use GPLv3.

'Microsoft's lawyers are not stupid, and next time they may manage to avoid those mistakes. GPLv3 therefore says they don't get a 'next time'. Releasing a program under GPLv3 protects it from Microsoft's future attempts to make redistributors collect Microsoft royalties from the program's users.'

That is not to say that software released under GPLv3 will be completely protected from patent holders. 'The only way to make software development safe is to abolish software patents, and we aim to achieve this some day,' Stallman writes. 'But we cannot do this through a software licence. Any program, free or not, can be killed by a software patent in the hands of an unrelated party, and the program's licence cannot prevent that.'

All that GPLv3 can do is limit the danger.
'In particular, we have tried to save free software from a fate worse than death: to be made effectively proprietary, through patents. The explicit patent licence of GPLv3 makes sure companies that use the GPL cannot turn around and use their patents to tell some users "That doesn't include you". It also stops them from colluding with other patent holders to do this.'

Ironically, the biggest obstacle to GPLv3 adoption is Linus Torvalds, creator of the kernel software that underpin Linux. Torvalds has stated he will not be moving the kernel from GPLv2 to v3, though his reasons are not entirely clear.

Stallman does not appear to be too concerned, since GPLv3 is designed to work alongside v2. 'There is no problem in having GPLv3-covered and GPLv2-covered programs side-by-side in an operating system,' he explains. 'For instance, the TeX license and the Apache license are incompatible with GPLv2, but that doesn't stop us from running TeX and Apache in the same system with Linux, Bash and GCC. This is because they are all separate programs. Likewise, if Bash and GCC move to GPLv3, while Linux remains under GPLv2, there is no conflict.'

However it will not be permissible to to combine code under GPLv2 with code under GPLv3 in a single program. 'This is because both GPLv2 and GPLv3 are copyleft licences: each of them says, "If you include code under this licence in a larger program, the larger program must be under this licence too." There is no way to make them compatible. We could add a GPLv2-compatibility clause to GPLv3, but it wouldn't do the job, because GPLv2 would need a similar clause.'

Stallman's defence can be read at gplv3.fsf.org/rms-why.html.