On Thu, Sep 11, 2008 at 12:19 AM, Jordi Gutiérrez Hermoso <email@example.com>
there are other ways you can satisfy clause 13, namely, the usual
channels of distribution that the GPL provides, plus a trivial network
server to indicate those other ways.
The license does not require you to provide your own "network server" to indicate anything. All you need is to include is a pointer to *a* network server hosting the code.
That is, if you're hosting a modified version of a game server, you're required to "prominently offer" players the URL of a location on "a network server" which hosts a diff of your minor changes, a tarball of files you've replaced, a VCS branch with your changes applied on top of the version you forked from, or a full copy of the version you're running.
This can be Savannah, shifting the hosting cost to the FSF/GNU if you feel it's too much. They'll gladly host your modified code for free, as will a number of different groups.
In the case of PySoy, we'll gladly host PySoy-based games, branch of our engine, or branch of any dependency. I see this as a convience to us and our users.