Not every program on gnutella has to be open source. The protocol has to but not the programs. Commerical program are a major part of gnutella, provide the best programs, the best improvments and most importantly competition between the programs.

With open source programs your not going to get the best people working on gnutella for nothing. And the people who do arent going to work on gnutella full time. There wont be any real competition because theres no incentive to be the best program. No competition means that the user will have less options and less features.

Plus a open-scource network wouldnt be able to compete with other comerical networks for the same reasons. The 100% open source program idea is a pipedream. Having some open source programs are important but all of them dont have to be. If all of the programs on gnutella went open source then i think gnutella will either die or fall so far back in competition with other networks that it will lose a ton of users that it wouldnt be worth using anymore.