The comment "It’s an open source encrypted, private alternative to other services such as Facebook chat." and then the comment from an alleged interrogator, “The interrogator (who claimed 22 years of computer experience) asked me which algorithms Cryptocat used and about its censorship resistance.” really set off some bells.
If it's open source, then git/svn/cvs pull a copy of the repo and read the code. No need to interrogate the guy. And second the DHS doesn't have any history of going after folks simply because they write some open source software.
Now could the guy be detained for other reasons? Sure. But this feels more like a troll to generate buzz for his app which seems to be on a few warez sites. My quick look at Github and Sourceforge didn't find it there.