I do agree with you that 4-clause BSD is open-source, but only just barely, and I agree with GP that it goes against the spirit of FOSS even if it is technically “open-source”.
Plus the advertising clause is just an obnoxious thing to have in a license regardless.
Yes but the advantage of Linux over windows is obvious. It’s open source. Where’s the advantage of FreeBSD? Companies can make their own proprietary fork and give nothing back?