Hey Chris, you do not have to release your source code, just because most Linux guys do, not every program is GPL. You just need to include a license that says what you want it to say, ie. you can use this software for non-commercial use for free, the source code is not distributable, etc. etc. I am normally a Linux guy, I use win98 in DOS mode for DOSCab, and I would have no problem using your software under such a license. This is one of the few problems with the Linux community a few, and I mean a few, people are just jerks about everything ought to be free all the time (I disagree not every program needs to be free, just not so over priced that the program makes his/her money back on the first sale). I would definitly support this move if you choose to make it, if not I will continue using DOS with DOSCab.
Just my 2 cents worth,
Scott Adams