• https://www.gnu.org/philosophy/open-source-misses-the-point.html
• https://www.gnu.org/philosophy/floss-and-foss.html
• https://www.gnu.org/philosophy/words-to-avoid.html#FOSS

FOSS attempts to conflate two different positions on software by presenting them as one entity. FLOSS is a better term for pure neutrality's sake but still falls in the same trap (attempting to send meaning as acronym/conjoining two historically different movements). Free software advocates do not bother with a neutral term because we desire a world of total software liberation and an ultimate death to non-free software. Open-source movements seek to collaborate with proprietary software or at the very least not to get in its way (it seeks olive branches over systemic change). Each group's rhetoric serves to reflect this fundamental difference. There is an overlap in both movements, but each person has to choose between compliance to the status quo or fighting to break it altogether.

Look at it this way, hypothetically, if it turned out that the Linux kernel was objectively the technically superior computer kernel to have ever existed and will ever exist and everyone in the entire world knew this: we would still end up in the same exact status quo because corporate oligarchs are already allowed to use the kernel to subjugate their users (nonfree firmware, tivoization/weak copyleft, proprietary userland) and have enough leftover propaganda (what they call marketing) and staying power to ensure their survival. Or in other words: if Linus Torvalds, the man who figuratively holds the keys to the most successful open source project in the world (that powers the entire internet) is still subjugated by firmware blobs and nonfree drivers, what chance do we have with these unethical firms?

FOSS is… Literally as you described it ... It’s pretty obvious.

Please don't reduce decades of uncomfortable and complex history to what is a marketable buzzword. I doubt we disagree all too much here, but the goal is to educate, not condense and dilute.