[citation needed] In 2009 a new different version of MCL has been open sourced: RMCL.
[2] RMCL is based on MCL 5.1 and does run under Rosetta on Intel-based Macs.
MCL was famous for its integration with the Macintosh toolbox (later: Apple Carbon), which allowed direct access to most of the Mac OS functionality directly from Lisp.
This was achieved with a low-level interface that allowed direct manipulation of native Mac OS data structures from Lisp, together with a high-level interface that was more convenient to use.
Over its history, MCL has been known under different names: Running on 68k-based Apple Macintosh Computers: Running on PowerPC-based Apple Macintosh Computers: It has also spawned at least one separately maintained fork: