Let me answer your question from a developer's point of view:
Spark is developed with Java Swing, which is a technology from 1997 and by now dead and unsupported, (I mean it's no longer developed by Oracle, no bug fixes, etc... afaik).
If a developer spent his scarce free time to develop something (for free), he most likely wouldn't put his work into an old and dead technology.
Developing in one's free time is also always about learning for yourself and learning dead technologies isn't attractive obviously.
Even if there was a student (as wroot suggested), he surely wouldn't spend his time learning Swing.
At least that's my reasoning behind the lack of development.