The mods are definitely wrong, and they shouldn’t be deleting posts here. But you could also be wrong, I don’t have the original posts to go off of, but I do have this one.

FOSS is not the same as Free Software, it’s a combination of Free Software and Open Source software, meaning it applies to both. In long form, it’s Free and Open Source Software, meaning it applies to things applying to one or the other, and not necessarily both.

If you mean Free Software (i.e. the FSF/GNU definition), then use that term. If you mean Open Source (i.e. the OSI definition), then use that term. If you’re not sure which you mean, but you know you mean one of the two, use the term FOSS. If you just mean the source is available but it doesn’t necessarily fit the the Free Software or Open Source definitions, use the term “source available” and leave it at that.

Most FOSS licenses are both Free and Open Source (i.e. they meet the definition of both), but not all. Many Open Source licenses are incompatible w/ Free Software licenses, for example the Apache 2.0 license is incompatible with the (L)GPL < v3 in some cases.

In general:

• FOSS - preferred when the software is either free software or open source software
• source-available - preferred when the software is not FOSS, but you do have access
• proprietary - use for either source-available or non-source-available software
• Free Software - use when referring to copy-left software (yes, it applies to more, but let’s keep things simple)