I'm glad that the title is what it is here. I sincerely and whole-heartedly believe in what SDF does as a non-profit. Anyone has the ability to go learn UNIX based systems without worry thanks to the SDF. No fear of ruining your own system, they have safeguards to keep you from ruining the pubunix, and the BBS community is fantastic.
Please, if you consider the ability for anyone to be able to try and learn a UNIX based system please donate. It keeps this instance running and is a free educational tool. https://wiki.sdf.org/doku.php?id=how_to_donate