JabRef is currently 2.10. This was released in 2014. The current version is 5.2, it's probably long overdue an update.
What would it take to get this updated?
The sources do not build with virtual/jdk:1.8. Upstream is recommending to use JDK 13 [1] which we do not have in portage and the most recent JDK version in tree (11) is not yet unmasked. At the moment we cannot add gradle based JabRef builds to portage unfortunately. [1] https://docs.jabref.org/installation#building-from-source
*** This bug has been marked as a duplicate of bug 600698 ***