Macos – Is Mac OS X open source

What exactly is Rosetta? (I have an idea, but your expert answer is probably better than my understanding.)

Rosetta is a piece of software through which PowerPC code can be run on an Intel Mac.

Why don't I already have Rosetta included with my new Snow Leopard install? Why would Apple decide to not include it? Would this have been an optional install from my Snow Leopard DVD, or is it only available online from Apple?

Snow Leopard is Intel-only. Apple essentially wants the few remaining developers who still have PowerPC-only software to recompile it for Intel. Rosetta is an optional install which is available on the Snow Leopard DVD.

Why would a relatively recent installer such as Adobe Flex Builder 3 require Rosetta? Is Adobe doing something silly?

Adobe's Mac range is possibly the worst-made set of applications that anybody actually uses. See Adobe UI Gripes for more Adobe hating.

Is there any performance or other impact or concern with having Rosetta installed?

Only when you're running PowerPC code. Simply having it installed will not decrease performance. There is little reason for you not to install it; it's a small package that allows some software to be run slowly that otherwise couldn't run at all.

I've made this CW so please edit this if you have something to add.

This is a shot in the dark, but are you using Mozy for backup? I helped another user with a problem where his kernel was running out of IPC-related resources (specifically Mach ports in his case), and he ended up tracking it down to Mozy.

See Some Mac applications crash frequently, with "__THE_SYSTEM_HAS_NO_PORT_SETS_AVAILABLE__" in backtrace

Even if you're not using Mozy, you might try what he did and turn on the "Ports" column in Activity Monitor and see who's using up Mach ports. Obviously you'll have to do this before the problem happens, maybe leaving it open so you can monitor things for early signs that things are about to fail. You might also turn on the "Messages Sent" and "Messages Received" columns to see which process are sending and receiving the most IPC messages. But before you get surprised at all the messages to/from the kernel_task, be sure to compare to a machine that's working normally, that was rebooted at about the same time, to get a baseline. You can also look at the list of processes in Activity Monitor to see if there are excessive copies of a given binary running.

Since you seem willing to dig into kernel sources, you might also want to read up on how to debug kernel problems:

• Apple's Mac OS X Kernel Programming Guide
• Technical Note TN2063: Understanding and Debugging Kernel Panics
• Technical Note TN2118: Kernel Core Dumps

After reading up on kernel debugging, you might try setting sudo nvram boot-args="debug=0x144" to enable several popular kernel debugging options, and then, the next time the problem hits, you can press your power key to force a kernel panic so you can attach with GDB from another machine and poke around. If you want your power key to go back to normal operation, use sudo nvram boot-args="debug=0x140" (leave the other cool options, on, but disable the power key hack) or sudo nvram -d boot-args (remove then entire "boot-args" NVRAM variable).