Folks. i compiled all my kernels with Xcode 3.2.6 under Snow Leopard! You must be sure 1) to download GCC for Snow Leopard GCC-10.6.pkg; 2) that all dependencies are satisfied http://shantonu.blogspot.com.br, and; 3) that all -werror flags are wiped out (do a search for it inside the XNU folder and wipe them all out!) before you start building.
But yeah! Do it! Try building yourselves! The more people become familiarized with this, the more valuable insights we'll have for what we want. It's fun. Worths the effort.
We're having some issues with making the userland to boot: that's why all of us are stuck in "Kernel is LP64". Possible causes we're examining (among others):
1) The ssse3 emu aren't still working like it should;
2) Sysenter issues (I looked for sysenter instructions and found none, but whatever);
3) Issues with some launchd process.
P.S.: Delta, AFAIK the access to developer tools like Xcode is and will ever be free. You just have to register with your Apple ID and download the software. But i prefer Xcode 3.2.6
XCode 4.2 for Snow Leopard can now only be downloaded from paid subscription dev account. When Lion wasn't released, it was free for everyone or something like that.
But now, with free account @ Apple dev, you can only see 3.2.6 for SL.