Free Software vs. Open Source Software.

I was a bit confused about what the difference is between FS and OSS. So I have been reading up on it. I’ve read about 5 different articles, and I’m still not sure what the difference is. Free Software does not mean software that you pay Zero money for as this article points out (by Richard Stallman.)

Free Software briefly means that you have the “freedom” to use, redistribute, study, modify and improve the software.

Which is similar to OSS. So far, I believe that the main difference is that “Open Source Software” sounds cooler, and is easier to market than “Free Software”. And that is the problem, as I understand Stallman tries to point out: market share should not be the primary goal, but the primary goal is the freedom itself that FS/OSS provides. So in this quest for market share, some freedoms are being sacrificed. (Such as using non-free software with the GNU/Linux, and all the problems that might entail.)

So to rephrase my current understanding of this issue: the primary difference between the FS and OSS philosophies is that FS refuses to use non-free software even when there is no alternative. (Please correct me if I’m wrong .)

Myself, I don’t know what non-free software that I’m using on my machine other than the Flash plugin, and maybe some codecs. (I wonder if there are Free flash and realplayer alternatives for Linux?) Maybe there is more to this issue than I currently understand.