Threadmil
Threadmiλ is a threads and concurrency library that provides implementations for several concurrency tools in a number of different CL implementations. It is a fork and a re-implementation of Bordeaux-Threads, with several extensions (especially, barriers, timers, timeouts, etc.), tests and semantic clarifications.

License is MIT.

Documentation: https://threadmil.common-lisp.dev/.
Repository: https://gitlab.common-lisp.net/mantoniotti/threadmilambda.