It’s not just mere acknowledgement. These versions of MacOS were, if I remember correctly, paid software upgrades. Making these previously paid released available for free download might not have been bureaucratically trivial. While it may seem like a trivial gesture a decade on, it's actually quite decent and very much unlike Apple to be so considerate towards users of 'vintage' hardware and software.
Edit: Yes, I did remember correctly. Mac OS X 10.9 "Mavericks" was the first version that was distributed for free to all Apple computer owners. Lion (10.7) and Mountain Lion (10.8) were definitely paid upgrades.
It wasn't back when software was distributed on physical media and there wasn't this "update culture". You were expected to update to a newer version of an OS if you want to, not because you have to in order to keep the ability to use the internet on hardware you already have.
This is a really glib view of the vast and complicated reasons people are encouraged to update their OS. It's not mere whimsy that in a rapidly developing malware landscape, updating your OS is a necessity.
Security patches are one thing. The constant moving things around and putting "fresh coats of paint" onto everything without solving any real problems is another.
But then, at some point, all mainstream OSes will have been rewritten in memory-safe languages and there won't be any more exploitable vulnerabilities remaining. What then?
Memory-safe languages do not guarantee absence of bugs or security issues. I remember when Heartbleed was discovered, and people were groaning how that would never have happened had OpenSSL been written in Rust, one of the OpenBSD developers wrote a blog post to explain how Rust's memory safety guarantees would not have prevented Heartbleed or a comparable bug.
It would no doubt eliminate a lot of bugs, but security researchers and black hats would almost certainly continue to find exploitable bugs. It would just get somewhat harder. But AFAIU, finding exploitable bugs at the OS-level has been getting progressively harder for a long time, to the point that these days the main attack surface are web browsers and users who unquestioningly open file attachments in email.
And people who eagerly add new features to operating systems will no doubt provide a generous supply of security problems to discover and "fix in the next release". ;-)
If that last bit truly isn’t a joke, let me be the first to point out that moving to memory-safe languages will not eliminate vulnerabilities. It won’t even really be close.
Formal proofs of correctness would probably get us closer to software that is bug-free, but literally nothing is a panacea, and at the scale of attack surface we’re dealing with most of the extreme options (even including “rewrite it in a memory safe language”) are too big to foresee happening in the short or mid-term in any meaningful way.
But most are, and they usually are most devastating. Mistakes in logic can sometimes be vulnerabilities that could, for example, disclose some information to an unintended party, but I can't imagine how one could lead to remote code execution.
Yes. Not so long ago it was possible to download system6 disk images directly from a simple html page hosted on apple.com This was quite handy for emulation.
