I finally got it to compile. Here's the trick for anyone else who is having a similar issue.
First, you'll need wxMac 2.8.2 found here: http://www.wxwidgets.org/downloads/
Then you need to follow their compile instructions for 10.6: http://wiki.wxwidgets.org/Development:_ ... ow_Leopard
Next you'll need libusb 0.1.* and it must also be compiled with the arch i386 flags. I couldn't get it to compile properly but I did find a compiled binary and sdk over here: http://www.ellert.se/twain-sane/
This is what solved my issue.
Finally, of course, you need to set the same arch i386 flags in wxsoft/macosx/makefile
Probably you'll also want to change the /opt/lib to /usr/local/lib I also removed -Werror because I'm lazy and didn't feel like resolving typecasting issues.
In a few of the c++ files, you'll have to resolve some issues with includes and class prototyping but that's all pretty straight forward. There's also some windows-specific code that you might want to put a #ifdef WINDOWS around.
but yay! Compiles! Ship it! ^_^