The package was created by Thomas, but it looks he's not interested in working on this currently (or just have no time). Problem is that current calendar plugin version will probably not work with Roundcube 1.3. It also requires some manual packaging work for Elastic skin support. Also there are some known issues in the database driver noone have time to work on. From Kolab perspective we could spend that time better on other things. Maybe after the final 1.4.0 release I'll do something about the situation, but I can't promise anything.