A creative accident happend when I launched an app on 10.6 that was built on 10.10 in a similar way like Cactus (Python & PyObjc).
It ran.
So after compiling way too many libraries I think I have my build environment and Cactus in a form that allows building on 10.10 and running on 10.6.
So here it is: 64-bit Cactus built on 10.10 running on 10.6:
It's obviously the file named "Cactus_074-64-for-10.6.app.zip"
-karsten
P.S.: It's not thoroughly tested. I just ran all my typical uses and found no behavior different from 10.6; apart that it feels faster