The Opal Library is a part of Pow. Pow is an free Oberon-2 compiler with integrated programming environment. You can download Pow including source code from http://www.fim.uni-linz.ac.at/pow/pow.htm.
I translated the Opal Library to Component Pascal for BlackBox and Juan Antonio Ortega gets the whole subsystem running. The modules String, Float and Utils runs inside the Blackbox environment. All other modules runs as stand alone applications only. We recommend to link the programs into a separate exe file to execute them.