Unison is no longer under active development as a research project. At this point, there is no one whose job it is to add new features or fix bugs.
However, Unison is still widely used (including by its original developers, who use it daily). It will continue to be maintained and supported for the foreseeable future, and we will occasionally release new versions with bug fixes, improvements (sometimes large ones), and contributed patches.
The Unison developers also sometimes take on larger projects to add significant new features on a consulting basis. Contact Benjamin Pierce if you need something from Unison that it isn't currently providing and are willing to pay to see it implemented.
Reports of bugs affecting correctness or safety are of interest to many people and will generally get high priority. Other bug reports will be looked at as time permits. Bugs should be reported to the firstname.lastname@example.org mailing list.
Feature requests are welcome, but will probably just be added to the ever-growing todo list. They should also be sent to email@example.com.
Patches are even more welcome. They should be sent to firstname.lastname@example.org.
Since safety and robustness are Unison's most important properties, patches
will be held to high standards of clear design and clean coding; feel
free to ask for advice and feedback on unison-hackers.
If you want to contribute to Unison, start by downloading the developer
tarball from the download page. For some details on how the code is organized,
etc., see the file CONTRIB.