Dahlia will be a retreat participant list mangement tool. It will track participants who are scheduled to attend retreats along with those who are on waitlists for retreats. The intent it to make the management of the waitlists easier and more streamlined. The process is very manual at this point and has just a few rules regarding handling.
Currently the org is doing all this work manually in Word docs.
Check the issue list and the discussion group for recent conversations about what's happening and what's needed.
Check the getting started wiki page for instructions on how to start working with the code base.