I was a bit too optimistic. The Makefile was not updated to deal with the calls it gets from pack_install/1 and there where some issues with Unicode handling that break the tests (and some more). Updated. If you pull SWI-Prolog to the latest git it will also nicely install scasp, either in the same directory of swipl or in ~/bin if one of these is writeable.
So, to install the system
git clone https://github.com/JanWielemaker/sCASP.git
cd sCASP
swipl -g "pack_install(.)" -t halt
Which should give you library(scasp), etc. to use the system from Prolog and a scasp executable in the current directory that is optionally linked from your preferred directory in $PATH.