The organisation had set a deadline of March 2007 for releasing the final version of the licence.

The head of the Free Software Foundation, Richard Stallman, says they are behind by a few months. The FSF and GNU are sister organisations.

"We were supposed to release the third draft in January, and we have not yet done so," Stallman said in reply to a query. "We are almost ready to release it, and we are working on the explanations that need to be released with the draft."

The existing version of the GPL was released in June 1991. A number of well-known software projects release their output under this licence, with the best-known among being the Linux kernel.

The revision of the GPL was undertaken to plug certain loopholes which have allowed companies to abide by the letter of the licence and yet violate its spirit.

The classic case cited is that of the Tivo, which runs on a modified version of the Linux kernel. Source code for the kernel and the software that goes to make up its operating system is available, but if one were recompile the kernel then it would be impossible to use it as the Tivo is designed to shut down if modified code - not authorised by the company - is used to try and run it.

The GPL version 3 will insist that if someone sells a software binary then, since he or she is also required to provide the source, along with that comes a requirement to provide whatever it takes to authorise a recompiled version to run.