It's a wiki containing the Trillian plugin API (including 3.x, which hadn't been documented on the old version of the docs), and intended to provide a general place for Trillian Developer sorts to store reference information, sample code, and so on.
I now know a lot more about Mediawiki templates than I ever wanted to. But I'm pretty pleased with how the thing came out!
Whew. Backed it all up, too, before I posted the announcement to the Trillian forums. Just in case someone decides to try and deface it or whatever.