Ok, maybe this is not the right thread, if so, please point me to the right one.
Some background: I've seen other Open Source projects derived from FreeBSD (FreeNAS, PFSense, etc) that called themselves "an OS".
They do give (marginal) credit to FreeBSD, but apparently they have little or no modification to the OS itself, and instead they appear to be just a "FreeBSD base OS" plus a collection of other open source packages, custom configurations, a suite of middleware scripts and a web frontend.
Because of that, I would say they are not an actual "OS" but more like a 'suite of apps' built on top of FreeBSD.
A good example would be FreeNAS, which rely heavily on Python and Angular to provide a user friendly way to do the same things FreeBSD alone can do from the shell.
They do present themselves as an "OS" (their website states "FreeNAS is an operating system that can......")
Now, my question: To which extend someone can use a FreeBSD base OS, modify a couple of things here and there, add some apps to it and legally call it a "BlahBlah OS" (with a different name, branding etc).?
This is a technical question and a legal one as well, Im not well versed on the practical applications of the FreeBSD license, but Im sure some of you are and can put it in plain language.