The Hedgewars Forum is here.
Hedgewars IRC channel
Development Mailing List
You can send emails to the official Hedgewars Development Mailing List where all developers and contributors can read your message
Important: you need to be subscribed to be able to post in the mailing list!
More info and public archives are available here: https://mail.gna.org/listinfo/hedgewars-dev
IMPORTANT NOTE: Please be aware that by sending in patches you grant unC0Rr (the project leader) all rights to the code (and any patents you may hold on it) and assets included in the patch. That implies that your code will be made public under the GNU GPL2.