Is there a Foundry chat channel in game that one could read/ask questions in while making/testing foundry missions?

I don't know about in-game, but StarbaseUGC keeps an IRC chat here. There are usually a couple seasoned Foundry authors in there who would be more than happy to answer any questions you may have.

At one time or another there were some chat channels. Problem is that unless you're testing a map there's no chat window, as a consequence they never got a lot of use. A lot of authors congregate in that chatroom on Starbase UGC.

It would be nice if they added chat functionality to the Foundry, as long as there's some way to minimize it so it wouldn't be distracting if you're really focused on something and didn't want to be bothered.

While we're at it, it would also be nice to be able to invite other Foundry authors to your map to preview it. That seems like it would be a logical extension of having an in-game Foundry chat room.

Neverwinter's foundry has the chat in it

http://tavernugc.com/screenshots/#more-63