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.
The Foundry Roundtable live Wednesdays at 7:30PM EST/4:30PM PST on twitch.tv/thefoundryroundtable "I would rather take a chance on getting a change made to the game through positive engagement than know for sure that I got a change made by complaining" -drogyn1701, May 14, 2014.
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.