I need a bit of clarification with something. The source code to the rzip program is licensed under the GNU General Public Licence version 2.0, but is the actual format specification covered by this licence too? The awkward problem is that the rest of my library that would possibly use RZIP (as a Delphi translation) for a couple of functions is being licensed under the GNU Lesser General Public Licence version 3.0.

Well, I think I'm pretty sure that rzip as a whole is covered by the GNU GPL, meaning the only way I can support it in my archiving format (at least in my GNU LGPL implementation) is to write temporary files and then pass them through a standalone rzip executable. For individual files i think that will be okay, but for solid compression it might be bit prohibitive, since that data could run into several gigabytes.

I must ask though... is the use of temporary files considered sharing data?

you could always email the author and ask him of his opinion on what you're doing. (He is the only one who can cause problems for you if he disagrees with your interpretation of the license)

a lawyer could possibly give you a better interpretation of the license but being right doesn't necessarily keep you out of court. (It will help you win in court though)

GPL licensed software have been used with proprietary software in the past (the use of DOSBox for repackaged commercial games is a rather recent example) so I'd guess that atleast some opensource developers would consider it ok if it is kept as a standalone executable.

You could also ask the author if he is willing to provide the necessary portions of his code under a more permissive license (such as the LGPL).

I agree with Simon. Contact the author and ask. It doesn't matter what we say or even what a lawyer tells you, that won't stop the author from taking action if they think you are doing something wrong. Asking will let you know exactly where you stand and avoid any possible problems.

Okay - I'll ask the author. Thanks for the responses, SimonForsman and Obscure.