Free Linear Programming Software?

Chao-Kuei Hung asks: "I will be teaching a freshman level math class next semester in which half of the course deal will deal with linear programming. I found a number of linear programming software packages from this website, but none of them seems to meet any of the FSF/OSI/Debian's definition of free/open source software, although some come with source code and some cost $0 for educational use. Does there exist truely free software for this topic? Are there LP modules/plug-ins for things like octave, rlab, or R?"