JRDF 0.5.6 has JSON SPARQL support and many things got a good refactoring including the MergeJoin (which now looks more like typical text book examples - for better or worse). The upgrade to Java BDB version 4 has improved disk usage and performance mostly around temporary results from finds and the like. The next version will include named graph support.
I'm considering this being the last version to support Java 5.
This release was also about learning things like Hamcrest, JUnit 4.7, various mock extensions (Unitils, Powermock and Spring automocking (which didn't make it due to not being able to mix and match runners). This seems to be a design flaw that I've been encountering with JUnit - you can't mix and match features from various runners. Even Powermock and JUnit's Rules (for exceptions anyway) was problematic. The answer was to go back to the inner class block version.