Just thought I'd make an app where you can control stuff with apple scripting when I came across the idea of PyObjC, but going to pyobjc.sourceforge.net shows it hasn't been updated since late 2009.
Does anyone know if pyobjc is still a valid thing to use?
Yes, Python-ObjC still works very well. I use it in a number of my scripts to work with Plists, and to call ObjC methods.
Apple has shipped Python-ObjC bindings in their OSs for quite some time now, so nothing more is needed for at least 10.5+. The bindings for Python and Ruby are well maintained, while the Perl ones seem to be lagging. It should also be noted that MacRuby ships standard with Lion as well (very exciting direction there... even though I am not a ruby programmer).
Note that if you want templates to create Python-ObjC, Ruby-ObjC, or Perl-ObjC applications you are going to have to dig them up from the open-source projects, as Apple has discontinued those templates in XCode. I have not tried on XCode 4, but in later versions of XCode 3 you could still drop the template files into place and they would just work.
Not if you want to use Python 3.
I don't know why you bring up Python 3. Lion does not include Python 3, and there are no Python-ObjC bindings for Python 3 that I am aware of from anywhere.
also, does anyone know if you can write the core of your application in objc and c/c++ and then use apple script obj c to build the interface for it?
Technically this is probably possible, but this would be an astoundingly bad decision to go that way. The methods to bind ObjC through XCode are a pure pleasure to use. Everything else is work.