Mainly targeted for the devs here, but speculations are welcome.
Why is Spiral Knights run on Java? Since Spiral Knights's release, was there any any consideration for an engine overhaul? Is the dev team and more generally, Three Rings, more comfortable coding in a certain language Java would provide over any other competitors?
Judging by their past works, such as puzzle pirate, and doctor who thinging magigi, I would say yes, Java is their area of expertise, or only expertise.