ECL
Embeddable Common Lisp, a member of the KCL Family, is a Common Lisp implementation initially developed by Giuseppe Attardi, maintained for many years by Juan Jose Garcia-Ripoll and currently maintained by Daniel KochmaƄski. ECL is the successor to EcoLisp).

It is a small but complete implementation which features a very small bytecode interpreter, compilation via C, generation of standalone executables and DLLs, loadable binary files, CLOS, CLX, sockets, and more... The areas that need work are

  • improving the extensions
  • improving the compiler and the performance
Project page is located at https://common-lisp.net/project/ecl/. ECL runs on Linux, FreeBSD, NetBSD, OpenBSD, Windows (Using Mingw and Microsoft Visual C++), MacOS X/Darwin (x86 and PPC) and Solaris (x86 and Sparc). It supports threads on all operating systems. Experimental builds for Android, NaCL and iOS exist.

I compiled it using mingw gcc under win32. threading also works under win32 making it the best free common lisp implementation available on that platform.

There is also a FreeBSD port to install it from and an X-Chat Common Lisp Plugin.

A package for NetBSD is available via pkgsrc.