Another good candidate is Richard Stallman. As founder of the GNU movement in 1984, he wrote most of the Linux environment, except for Linus' kernel. This includes the GNU Compiler Collection and Emacs. While at MIT he wrote an OS in Lisp that was commercialized in the 70's. He published important works on Artificial Intelligence while at MIT. It was he that coined the name POSIX.

Most people know him for his advocacy of free (as in free speech speech) software. He started this advocacy at MIT by personally decrypting users' encrypted passwords and suggesting that they change them to the empty string! When Xerox refused MIT users the source code for the newly installed laser printer, he rewrote the driver for the old printer to include undreamed features.

Through his amazing mastery of programming and force of will, he created a whole sub-culture in programming and computers. See Richard Stallman

Of rms’s many pearls, my favorite is:

“With software there are just two possibilities; either the user controls the program or the program controls the users.

The first case is free software because, in order for the users to have effective control of the programs, we need certain freedoms. Those freedoms are the criteria of free software.

If the users don't control the program, then the program controls the users, and the developer controls the program. That means that program is an instrument of unjust power.” See An interview for OUGH!