Thank you for your ideas. We started to use Phex and it seems to do the job. But we will definitely try some of your recommendations.

The reason why I want to use Gnutella and not a central server is mainly network bandwidth. We are developing software (70 programmers) and have to distribute new builds frequently (and branches etc.). A build has about 800 MB. If everyone fetches 800 MB from the server, things slow down significantly.

Actually it's even worse. Traditionally the compiler runs on a local machine and accesses C++ files on the server. Because of include file nesting many include files are accessed multiple times, which increases the total network use to even more than 800 MB. This results in turnaround times (edit, compile, execute) of about 60 Minutes.

Gnutella seems to be a rather efficient solution to this problem. Using faster equipment (100MBit Ethernet, faster server, switches) may be even better, but it takes some time and a lot of money to install it.