http://y7yea4pmqqtznb33qiugvysyn2bob5v62e4pvoadoibrwkq3tsddjeyd.onion/ps/glossary/open-source-software
While it is known as “free software," it's not necessarily free as in zero-cost: FLOSS programmers can ask for donations, or charge for support or for copies. Linux is an example of a free, open source program, as are Firefox and Tor.