After HipChat got closed down earlier this year we evaluated a few alternative chat solutions. During this period we temporarily moved community discussions back to IRC (#wildfly on Freenode).
We found that Zulip worked well for us and have now settled on this as our main chat tool. Thanks to the people at Zulip for their open source license!
To join in, go to https://wildfly.zulipchat.com and sign up. The most obvious stream to join is #wildfly-users for user questions. If you want to get involved in development, or keep tabs on what we are up to, #wildfly-developers. We also have more specific streams for development of larger app server areas (e.g. #wildfly-elytron and #undertow).