A 100% Java Warren Abstract Machine implementation.
jWAM is a 100% Java Warren Abstract Machine implementation. Currently it is still under development though all the basic functionalities (compiling, resolution) are working. As far as I know this is the only open source Java based implementation out there that does not simplify Warren's design.
I have done some comparison's with other Java based Prolog engine's and jWAM does seem to outperform them all quite well (tuProlog, JLog, JIP, jTrolog).
OpenPoplog is a multi-language, incrementally-compiled virtualmachine-based development environment with its own extensive teaching and support material, supporting the languages Pop-11, Prolog, Common Lisp and ML on Unix, VMS, Linux and Windows.