Well, I read there is some agreement

Yes there is a need for cooperation. This must be on a shared code basis. Standard functions can be the best. If one group decides that a certain function is to be proprietary, and it fits in in the way of plugins/module or whatever fine When another group decides that the "universal" client needs that function everywhere, it only needs a OS version that connects in the same way.

Point is licensing, copyright.

You guys are no lawyers. Neither am I. But to get to the same codebase for the client, you need to think about it.

Open Source authors have currently the right to post the same code under a different license as well. Given the huge amount of clients there is plenty code to start with.

If you want your Gnutella business to survive, make your business a legitimate business. Think technology, Think on how you make money with P-P. Work that in your commercial offerings. You will find that the client will also need work to enable that. So you will NOT stop developping the client. Everyone (interested in Gnutella) will win. And a RIAA/et al will have a problem with you as a target because
* The user is responsible in analogy with a car a gun.
* You as a business aim to make money on a legitimate offering
* Improvements that are clearly to enhance the "illegal" use, are done by a "anonymous" Open Source Community. AND those improvement can be in the form of a plugin/module whatever..

Thanks,
have fun
Gerard