Actor-model library, framework, or language written in C?

Question

The Actor-model was defined in a 1973 paper by Carl Hewitt, but has been popularized by the Erlang language. I believe the parts of Erlang that aren't self-hosted (written in Erlang) are written in C; BEAM and HiPE are written mostly in C. What are some alternative Actor-model implementations (languages, frameworks, or libraries) that are written in C?

Answer 1

There is libactor which is a GPLv2 library implementing the actor model in a single process using pthreads.

Answer 2

Consider libdispatch.