Stallman walked out of a well-paid job at the artificial intelligence lab of the Massachusetts Institute of Technology in early 1984 and started writing code for the GNU project because he was not willing to subscribe to the notion of writing code that could not be shared by anyone who wished to do so.
What drove him was the switch by MIT from the timesharing operating system which was called Incompatible Timesharing System to Digital's new non-free timesharing system. The change was necessitated by the march of technology - better, more powerful hardware created the need for newer software that could take advantage of it.
Ninety-nine out of a hundred people would not have had a problem with using a proprietary system at work. A large number of today's GNU/Linux users are forced to work with Windows or the Mac OS X at their offices.
The reason why free software has such a massive profile today - and has given respectability to the term open source - is because of that 100th person, the oddball who refused to bow to three basic assumptions - "...that software companies have an unquestionable natural right to own software and thus have power over all its users...; that the only important thing about software is what jobs it allows you to do...; (and) that we would have no usable software (or would never have a program to do this or that particular job) if we did not offer a company power over the users of the program."
You can call the man eccentric, crazy or stark, staring mad. Stallman began work on his dream, a free operating system, in January 1984. By 1990, everything was ready apart from a kernel. The Linux kernel, which was first released in 1991, provided the missing vital bit. Stallman acknowledges this: "It is due to Linux that we can actually run a version of the GNU system today."
There is a stage in every great software hacker's life when he or she feels that his or her contributions should be acknowledged. For example, Steve Wozniak, one of the truly great hackers, wrote a book called iWoz in 2006 in which he removed any misconceptions people had over his technical role at Apple, a company that has come to be identified with Steve Jobs.
Stallman has always sought to have the GNU contribution acknowledged by using the name GNU/Linux instead of Linux. he is not incorrect - Linux is the name of the kernel. It is a reasonable request but does not find many takers, some arguing that it makes the name clumsy. His insistence on this name has not contributed to his popularity.
Stallman has other detractors too, people who release software under more permissive licences like those which the BSD operating systems use; code under such licences can be taken and locked away in proprietary programs, something which the GPL does not permit.