Cosmos can be installed by, (1). Installing Swi-Prolog (preferably 8.4+), (2) downloading the latest release, and (3) simply typing,
make
in the project directory.
This should work on any system that can run Swi-Prolog.
You can test that the installation has succeeded.
$ cosmos -v
"Cosmos 0.13 beta - (Pl)"
Cosmos can be installed as a Swi-Prolog pack. This is recommended if you are already a Prolog user or plan to use the languages together.
:- pack_install(cosmos).
You can then load the language.
:- use_module(library(cosmos)).
:- cquery('x=2').
If you want to open the interpreter:
:- cstart.
As said, this is recommended if you're already a Prolog user. You're opening the Cosmos interpreter inside the Prolog interpreter, and so on. This is somewhat redundant.
Naturally, you may install it both normally and as a pack.