A-A-P is a software installation system like FreeBSD ports and Debian apt,
but crossplatform.

Have anyone heard of this? It was suggested on the caml mailing list where
they are also struggling with deploying software.

http://www.a-a-p.org/

It appears that it could be both inter-OS and inter-language, although I
have not studied the details.

Larger projects could easily depend on packages from several languages, so
having a good Ruby install system that only works for Ruby is not the ideal
solution.

Mikkel