Version 2.11 beta 2 (May 19th, 2015)
I'll add the ebuild to the tree...
I have added a binary package to tree, =app-text/jabref-bin-2.11_beta_rc2. Please give it a try!
Adding binary packages is frowned upon yet we should strive for compiling software from source. What kept you from doing so? Do you need help Nicolas?
Upstream switched to using gradle for this build system. Gradle is not in tree yet.