ECL is now officially supported on the OSX/Intel platform. The source code is available as anonymous CVS only (See http://ecls.sf.net/cvs.html)
The initial port by Brad Beveridge has been complemented with some configuration flags that remove the need to use Darwinports and which port the SBCL-SOCKETS package to OSX. ECL on OSX/Intel passes Paul Dietz' test suite with about 36 failures, which is more or less what other the other ports do.
The only caveat is that the Boehm-Weiser garbage collector shipped with ECL (i.e. version 6.5) has some problems with threads in OSX. It is thus not recommended to use the configuration flag --enable-threads on this platform until these and other issues are solved.