Jython’s development is communicated through a myriad of ways, mostly through mailing lists, but also other forms.
The primary mailing list where discussions about Jython’s development occur is jython-dev. The list is open to the public and is subscribed to by all core developers plus many people simply interested in following Jython’s development. Discussion is focused on issues related to Jython’s development, such as how to handle a specific issue, a PEP, etc. Technical support questions should not be asked here and instead should go to jython-users.
Jython-checkins sends out an email for every commit to Jython’s various repositories from http://hg.python.org. All core developers subscribe to this list and are known to reply to these emails to make comments about various issues they catch in the commit.
There is a mailing list related to issues on the issue tracker. Subscribe to jython-bugs if you want an email for all changes made to any issue.
Some core developers enjoy spending time on IRC discussing various issues regarding Jython’s development in the #jython channel on irc.freenode.net. This is also a place wher you can ask for help with Jython, but the channel does not always have anyone around to answer. You can use freenode’s Web interface if you don’t have an IRC client.
Several core developers are active bloggers and discuss Jython’s development that way. You can find their blogs (and various other developers who use Jython) at http://planet.jython.org/.