the.com/free software
free as in speech, not free as in pizza — though it can be both.
means software you can run, study, modify, and redistribute, because the license guarantees those freedoms instead of just letting the vendor revoke access whenever.
from coined by richard stallman in 1983 after a printer at mit refused to share its driver source code, prompting him to launch the gnu project and the free software foundation in 1985.
four freedomsrun, study, modify, share — numbered 0 through 3
copyleft trickgpl uses copyright law to forbid restricting others
not open sourcestallman calls open source the same code, weaker ethics
gnu recursiongnu stands for gnu's not unix, a joke that stuck
for instance
linux kernel — started by linus torvalds in 1991, now runs most of the internet
emacs — stallman's own editor, still updated after more than 40 years
wikipedia — content free to copy and remix under a compatible license since 2009