I have compiled dogbert's CMI8738PCIAudioDriver.kext from source with XCode 2.4.1, and it works. I briefly looked into the source, and it looks safe and open source to me.
GENERIC CMI8738 DRIVER ---- ONLY FOR OSX86 Tiger 10.4.9 !!!
* For other versions compile from source *
0. login as root
1. Unpack CMI8738PCIAudioDriver.kext to /tmp/ for example
cp -r /tmp/CMI8738PCIAudioDriver.kext .
chmod -R 755 CMI8738PCIAudioDriver.kext
chown -R root:wheel CMI8738PCIAudioDriver.kext
3. Reboot -OR- try to load manually with: kextload CMI8738PCIAudioDriver.kext (Card info should be printed)
Driver provided here is for educational purposes only, without any warranty. Please support Apple by bying real Mac!
Just tried this on 10.4.10 (mac.nub.1) for a motherboard integrated cmi8738 and it works.
There was no need to compile from source (I couldn't have done it, anyway, since I don't have xcode). Just copied the kext to /System/Library/Extensions, run those commands and loaded it. I have only stereo output (no mic), but that's all I need.