Although Bordeaux-Threads may be more popular today, but Portable-threads offers more portable APIs (e.g. atomic-incf) and supports older versions of implementations. GBBopen also has a " scheduled-periodic-functions" module based on portable-threads, it literally supports creating "scheduled periodic functions" which is very useful in a Lisp server environment.
Dan Corkill is the one to bother regarding bugs, comments, criticism, suggestions, enhancements, and extensions.
Gary King is the one to talk to if something is wrong with the ASDF-Install portion of things.
Chun Tian (binghe) created a separated repository on Github after realized that cl-containers doesn't use portable-threads any more (the download link below is a very old version of portable-threads). This new repository contains both "portable-threads.lisp" and "scheduled-periodic-functions.lisp" from GBBopen project. He also added support for LispWorks 7.
Apache 2, compatibility layers