As part of the porting, though, are there security guarantees?
I imagine if they're re-written low-level implementation details they'll be opening themselves up to risk (not to mention the chance for backdoors). I wonder what their process is for fixing new security holes as they are fixed in firefox.
In any event, it is much more secure than running Firefox 3.5, which has published exploits.
We track ESR and occasionally backport later fixes. It was easier to do it that way than to have widget or gfx break on rapid release -- that way we have the entire ESR cycle to get it right.
10.4Fx does have a JIT. Right now it's a highly modified version of BaselineCompiler (I hacked BaselineIC to have better type and shape guards that take advantage of the greater ILP possible with the PPC integer unit), but I've had trouble getting our JaegerMonkey implementation to come into the Ion age. What we'll probably end up doing is blowing it up and rewriting it based on MIPS, since MIPS does many of the same things we have to and is much more like us than ARM (they do lui/ori to load 32-bit quantities, we do lis/ori; they have a link register too; they have similar branch stanza requirements). We have an unusually large stack as well, mostly for the stack frame requirements of the ABI. I hope to have this ready by 38ESR.
Security is a concern for the browser. I hate relying on security by obscurity, but as you say, we're a tiny segment of a tiny segment (while 10.4Fx will run under Rosetta, and some crazy people do, it's not our core concern). We don't run Flash or Java anymore because of Rosetta Flash and Flashback, or any other plugins, for that matter. Since Firefox implements NSS, that means we're not beholden to deficiencies in the Apple-shipped SSL or NSURL. Heck, since Mozilla implements its own media libraries, we don't have to rely on the system ones either. It's going to be a lot safer than a Webkit shell which has all of those dependencies and more.
PowerPC forever.
No, you're not. The next logical question would be: "So why don't you get a different OS?" There are dozens of FOSS OS's that will work just fine on your machine.
Apple is well-known for its rapid cycles of planned obsolescence, and technical users have no excuse for not knowing this. Either you keep buying their products on their schedule, or you say goodbye to their ecosystem. If you do neither, you have nobody to blame but Apple and yourself.
Why should Reddit keep supporting a Firefox version that was EOL'ed over three years ago and is known to be grossly insecure, just because Apple and you disagree about which Apple devices Apple's OS should support? That's a problem between Apple, Mozilla, you, and nobody else.
Strangely my Windows machines from the same era (and earlier) aren't caught in the same pile of issues. They're still running XP, but pretty much everything still more or less works on XP (at least things the machines are physically capable of running). I've toyed around with installing Win 7 on them, but really, what's the point? There's nothing I can't really do with those machines that's within their processor profiles.
I don't know what programs you use regularly that tie you to OSX, and can understand the need for them, that said, there are options that are available to you.
Have you considered installing a variant of Linux on it, so that you can use a new Firefox?
You can also buy Lion and Mountain Lion, too, as a code to use on the Mac App Store. (Presumably Mavericks will join them soon.) More info: http://store.apple.com/us/help/downloadable_software#MacOSX
http://store.apple.com/us/product/MC573Z/A/mac-os-x-106-snow...
https://www.debian.org/ports/powerpc
Looks like even the latest Debian 7 is supported.
https://www.debian.org/releases/stable/powerpc/release-notes
If they enjoy the challenge of maintaining old machines past their expiration date and don't mind dealing with the annoyances, then that is a total geek thing for sure (not that there's anything wrong with that). People doing this understand and accept the challenges of doing this, and usually don't go around complaining about it.
If they can't afford a replacement, there's always the "just put Linux on there" option, but it's unfortunate that they can't just get a new machine. This rarely seems to be the case in these discussions though, at least on HN.
The most common non-nerd reason for clinging to unsupported hardware seems to be self-defeating stubbornness or cheapness, where the person feels a compulsion to keep it going "for the principle of the thing", where it's almost like they're doing it out of spite. If they want to do this to themselves, fine, but it doesn't make it any less self-inflicted.
"Why don't you just get a new browser?" you might ask. Because new versions of browsers don't work on OS 10.4.
"So why don't you upgrade your OS?" Because as far as I can tell, no upgraded OS that will work on this machine is still available. There's no upgrade path from here to there. OS 10.6 would run on this machine, and OS 10.6 would run the latest Chrome, but you can't get OS 10.6 any more.
So I'm stuck in a bind, with no other option than to throw this (perfectly good) machine out completely. I do have a newer machine, but I keep it in the office, and this one ought to be capable of doing everything I want from it, but web devs keep breaking things that used to work fine.