While I am a little concerned about applying these fixes, it is clear that the previous behavior was broken and the initial set of patches as applied did not improve matters. The only risk I can see is that there is a slight chance that there *might* be some 3rd-party package that unknowingly depended on the previous behavior of setting MACOSX_DEPLOYMENT_TARGET globally and which might now fail.  There is no simple way to find such packages short of attempting to build them and test them.  However, if there *should* be such packages, the simple fix for them is to export the desired MACOSX_DEPLOYMENT_TARGET value into the interpreter process (via a shell variable, for instance).  So, I think it best to bite the bullet.  I've applied the Distutils patches to 2.7 (for 2.7.3), to 3.2 (for 3.2.1), to default (for 3.3) and the packaging patches to default (for 3.3).