I just came across this game today and thought it would be great to have this portable. It has a BSD License. The source is available and everything, but if the BSD License is too restrictive, even a launcher would be nice. There is a .zip dl for Windows, but I'm not sure if it's truly portable. Anyway, here's the webpage:
http://nooskewl.com/index.php?option=com_content&task=view&id=31&Itemid=26
Description (from the site):
"The Monster series of RPGs are high quality open source role-playing games. Built from scratch with a focus on good story, unique gameplay features, and professional looking and sounding artwork and audio. Monster 2, the latest edition in the series, is a nostalgic trip back to the days of the epic SNES RPGs like Final Fantasy and Breath of Fire."