kawa is unfortunately a somewhat shoddy project. Alot of halfbaked features / abstraction ideas (eg trying to support CL for whatever reason), dubious tooling for a java project (autotools), unclean and inconsistent code formatting. It's missing some features that are expected in a real scheme like multishot continuations; someone wrote research about it as a MSc thesis, but due to mentioned shoddiness its integration to upstream stalled and hadn't been merged.

At some point I thought of forking it to then cut out and polish the core, but then my attention got caught by graal's truffle framework as a plausibly better path for implementing scheme in java