The readme seems to suggest it uses reference counting and doesn't do anything special about reference cycles:

> Another thing is garbage collection. It seems to be the silver bullet of automatic memory management when it comes to scripting languages, but it has some definitive, serious downsides. Non-deterministic behavior is one, speed is two, memory overhead is three, the difficulty of a decent implementation is four. Reference counting is a simpler approach that is more lightweight, easier to implement, completely deterministic and it has no memory allocation overhead (a program uses only as much memory as needed). Refcounting has its disadvantages too (e. g. memory leaks caused by cyclic references), but I believe that its good properties outweigh them.