CatB and Open Source aren't coaxial, but there wasn't a very clean separation between them either: https://www.free-soft.org/literature/papers/esr/cathedral-ba... https://web.archive.org/web/20021001164015/http://www.openso... . "[T]he same pragmatic, business-case grounds that motivated Netscape" was CatB. Even now OSI doesn't emphasise any separation: https://opensource.org/about . You are correct: the Open Source Definition does not mandate an open development model. However that's probably at least in a small part because, well, how would one craft a legal requirement for open development in a software license that wasn't either unenforceable or very burdensome and abusable? It's also quite definitely because the expectation was that forks and/or the threat of forks would in practice enforce a certain level of open development on OSD-compatibly-licensed software: this was in fact what ended up happening to GCC at least once https://en.wikipedia.org/wiki/GNU_Compiler_Collection#EGCS_f... . If software projects all largely go the way Ladybird is going now, and stay that way, then it's a crushing (though not total) defeat for what the Open Source movement promoted and what it hoped to achieve; but sure, to be clear, Ladybird remains OSD-compliant. (Not total because at least the source remains available, without paying or signing anything, for bug-hunting.)