Four of the top five, six of the top eleven, and seven of the top twenty downloads of open-source software packages from Sourceforge are peer-to-peer file-sharing applications. (I've highlighted their rank and download tally below in red.)
If LimeWire, another open-source P2P file-sharing application, chose to distribute their application through SourceForge, it would be in one of the top spots, as well. (Download.com reports over 56 million LimeWire downloads.)