"giving users as much control as possible is beneficial to everyone"
Sounds like Open Source to me.
"parameters are determined by the organisation supporting it, and serve their goals rather than yours"
Sounds like a typical closed source proprietary client to me.
"Shareaza lets everyone optimise their own performance - now, and in the future as the Gnutella network evolves. You?re not stuck with some settings that were forced on you ?for your own good?"
And the only way you can assure "in the future" is to release your code to GPL so even if your company is gone the program lives on.
"I think on a free network like Gnutella it?s important to empower the people who are the network."
Open Source empowers the user in ways we haven't even thought of yet. It opens the door to more innovation and people who you never knew existed may jump in and code the next "killer feature".

The innovation is coming from the Open Source nature of Gnutella and thus to be complete with this whole concept, the clients need to be Open Source.