Thanks! The paper will be (tentatively) presented in October. We certainly want to have a release by then.
Open-source software from our lab (Graphviz being the best-known example) is usually EPL; we don't really have much saying on the matter. At the same time, the backend is a completely self-contained HTTP server, so I think you can isolate it from the rest of your stack without license implications. IANAL, obviously.
