I've updated the FAQ section with some questions we've been seeing.  Here're the changes:

How much leeway can I have on the test cases? If I have it say "ERROR" instead of "Err" for 1 / 0, is that still legal?
No leeway; your calculator must display the exact output we list. You can, however, have your program do other stuff outside of the calculator's display screen (using alert messages, opening other windows, etc).

What kind of system will the entries be run on?
Windows XP Professional SP 2 or NetBSD 3.1, 2 GHz with 512 MB memory.

NetBSD?! Why aren't you guys using Ubuntu Purple Poodle or some other obscure distro that no one other than me has ever heard of? I'm so writing an open letter on Slashdot about this...
No, dear god, please! Not an open letter! We'd be ruined! Just deal with NetBSD.

Is there an execution time requirement?
No operation should take more than several seconds. If you're afraid that your architecture will run too slow, email us a brief summary of what you want to do and we'll let you know if it's acceptable.

I have a question about an idea I have. I know you said to post it in the forum, but this is a really unique idea that I don't want the thieving WTF community to steal.
Oh, crap, we should've thought of that. Email Alex or Jake using the contact form and we'll get back to you.

We're trying to get the GTK solution up as soon as we can; expect it by the end of the week.