"Ordinarily, when you think of the phrase ‘free software’, the definition that comes to mind is a piece of tool that can be used or modified freely without any restriction.

" The idea of open source is that allowing users to change and redistribute the software will make it more powerful and reliable. But this is not guaranteed. Developers of proprietary software are not necessarily incompetent. Sometimes they produce a program which is powerful and reliable, even though it does not respect the users’ freedom.

“Open Source” advocate: «...I associate much more with the "Open Source" (also as Richard defines it) camp, and am open to the existence and use of proprietary software...» --

"Stallman makes a clear distinction between the free software and open source movements. The free software movement is based on values of freedom and social solidarity, he said, while the open source movement is thinking about practical benefits only, and forgets what’s most important..."

"Open source is a development methodology; free software is a social movement. For the free software movement, free software is an ethical imperative, because only free software respects the users' freedom. By contrast, the philosophy of open source considers issues in terms of how to make software “better”—in a practical sense only. It says that non-free software is a suboptimal solution.

"In February of last year, Richard M. Stallman, founder and president of the Free Software Foundation, spoke at the International Conference on Communication and Technologies in Havana about what he strongly believes are the merits of non-proprietary software. I recently learned directly from Stallman what that experience was like.

RMS: "Please do not use the term «open source» to describe what Emacs is in. Emacs is part of the GNU Project, which is part of the free software movement. To call us «open source» is like calling Kucinich a Republican.

See http://www.gnu.org/philosophy/open-source-misses-the-point.html for more explanation."

RMS: «When we call software “free,” we mean that it respects the users' essential freedoms: the freedom to run it, to study and change it, and to redistribute copies with or without changes [...] As the advocates of open source draw new users into our community, we free software activists have to work even more to bring the issue of freedom to those new users' attention.

We just published an article about contribution agreements for free software projects from our president Richard Stallman.