Blender 2.65 Cycles script not found

Hi,
I’m on Mac OS X 10.5.8 and for some reason, there’s no Blender 2.65 for that anymore on blender.org (even though they suggest Blender is available even for OS X 10.4). So I thought they suddenly changed something and just jumped up 2 versions without warning.

However, I came across a thread linking to buildbot, where they DO have OS X 10.5 builds, however, these do not have Cycles installed. It’s not available in the usual dropdown and when I look for it in Addons, it says ‘script not found’.

So where can I find this script and how do I install it?

And why isn’t this included by default? I mean, what’s the point of upgrading to 2.65 without Cycles? Might as well stick with 2.64 then.
Thanks.