PRIMA is under copyright of the Protein Laboratory, University of Copenhagen, and has a BSD-style license with clauses 3 and 4 removed.
Although OS/2 was the platform on which PRIMA was born, currently the most completed code exists for Win32. The X system-specific code is under very active development at the moment, and we hope to make it as good as the Win32 version before Fall 1999. OS/2 Presentation Manager-specific code is usable but outdated since much of the APC API has been changed during the last half year.
You should be able to download the latest version of PRIMA from http://www.prima.eu.org/. Currently PRIMA is not on the CPAN, but we hope to put it there soon.