Truth is, Google doesn't care what open source project you want to make into GSoC, as long as someone likes your proposal, the project will get the $$ it needs :) Note Mercurial didn't make it to GSoC officially this year (probably have to go under PSF's name) - so even popular OSS doesn't automatically becomes a GSoC participant.
Tor wasn't just sponsored by the Navy, it was "originally designed, implemented, and deployed as a third-generation onion routing project of the U.S. Naval Research Laboratory." https://www.torproject.org/about/overview.html.en
Truth is, Google doesn't care what open source project you want to make into GSoC, as long as someone likes your proposal, the project will get the $$ it needs :) Note Mercurial didn't make it to GSoC officially this year (probably have to go under PSF's name) - so even popular OSS doesn't automatically becomes a GSoC participant.