From the Reva Forth website:
There are plenty of full-featured Forth compilers: IsForth, BigForth, Win32forth, Gforth, and many commercial Forths. Reva is based on RetroForth, which is modeled after CMforth, Colorforth, Eforth and Pygmy. It uses some, but not all, of Chuck Moore's newer ideas. It is currently targeted at the Intel x86 CPU family, and runs natively on Windows and Linux. There is now the beginning of an ARM version, currently targeting the Windows Mobile platforms.
Reva is a free Forth implementation for Windows and Linux.