Clozure Common Lisp

From http://ccl.clozure.com/:

Clozure CL (often called CCL for short) is a free Common Lisp implementation with a long history. Some distinguishing features of the implementation include fast compilation speed, native threads, a precise, generational, compacting garbage collector, and a convenient foreign-function interface.

BeagleBone Black support is enabled with a patch published on the mailing list.