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Any development which is done on v0.9.x should, of course, also be merged into master. The cleanest way to do this is to develop on a personal branch which is branched off master at some point before today, and, when you're finished, merge that branch into both v0.9.x and master. (Careful: Not the other way round.)
Update: Apparently, there are issues with (I would guess) Bintray's delivery network. Currently, Maven artifacts will sometimes only download on the second attempt, failing some builds. Let's see how this develops.