Elona, a Japanese roguelike (available in English) has been around for years, but the original creator has decided to move on. He has, however, released the source code ( via a time-limited link in an announcement on the J side of the Elona forums) without any licensing restrictions.
On the English forums, there is a thread currently gauging interest in people continuing development of Elona. If you are interesting in on working on one of the more quirky roguelikes around, and know a programming language ( especially HSP or C/Java/etc ) you might want to check out the English forums!
If you want to take a peak at the source (it's in a basic-like language called HSP ) take a look at the topmost forum sticky on the J side of the forums ( you can also use google translate to help fumble through if you don't know Japanese. )
