I'm really tired (had a long day), so I'll only reiterate the difference between free software and open source today. Mainly because I've heard some people mixing them up here and there, not realizing there's a fundamental difference between them. I described this difference in "Free Software, The Religion":http://www.zefhemel.com/archives/2004/08/12/free-software-the-religion, but if you don't feel like reading that much text, I'll briefly mention the main differences. Free Software is about freedom, not price. They think it's evil to put any kind of restriction on the use of software. Well, nearly. You should be able to modify it, distribute it, use it in your own free software but it should remain free software and copyrights still apply. According to the FSF(Free Software Foundation), free software is the only ethic kind of software. If you develop proprietary (non-open) software, you're evil. It's as simple as that. The FSF's main license is the "GPL":http://www.gnu.org/copyleft/gpl.html. The GPL is a tool to spread free software. The FSF is a political movement, not a practical one.
The open source movement in contrast sees open software as the best way to develop software. Many eyes see more than just a couple. Therefore more bugs are found and the software is of higher quality. Being allowed to modify the code, distiribute it and reuse is something that's convenient. They don't necessarily think proprietary software development is evil, just that the open source way is a better development paradigm, and many companies are starting to see that. The open source movement is more of a practical movement than a political one. Being an open source developer doesn't mean you don't have the FSF's believes. Open source just isn't about political statements. All the stuff licensed under a GPL license is considered open source. Licenses like the "BSD":http://www.opensource.org/licenses/bsd-license.php one (which also allows you to use code in prepretary software) are open source licenses aswell.
My opinion is simple. I do not share the view that proprietary software is evil and don't see why all software should be open to everyone. And it's not ignorance, I've read "Free as in Freedom":http://www.amazon.com/exec/obidos/tg/detail/-/0596002874/103-8935409-7422208?v=glance and really tried to understand the reasoning behind it. I just don't share the beliefs. I don't like the zealot vision that free software has. That's also why I'm not a big fan of the GPL; because it's a tool to spread free software. Open source, on the other hand, I do like. I see many occassions where a more open development style is useful. And hey, sometimes it's just handy to have the source code so you can adapt it to better suit your needs.