Hey!  Yes I do most of the coding for our clan.

As far as GameSpy goes- I haven't had any notice from GameSpy about using their services without permission.  We've had the stats page public for more than a year.  As far as I know GameSpy has never publicly released specs for its query protocols, master server protocols and the SOAP database API.  Yet people reverse engineer and use them and I've never seen any direct action from GameSpy (well, other than the people messing with the cd-key validation from GameSpy).  It's good to see you're thinking about releasing a tool for UT3 :).

You're right about the achievements.  I see no way to grab achievements through GameSpy without logging into the player's account.  Steam does have a copy of the achievements though but I haven't looked into it too deeply.