There could be some compatibility problems with sharing the libraries. Although we didn't delete much in going from V2 to V3 (all I can think of are the V1 actors), a bunch of things were put into subcategories and otherwise reorganized. And of course you'd want to be careful not to lose any custom objects, poses, etc. that you may have added while using V2.
With those caveats in mind, FrameForge on the Mac can follow aliases to the Object Library and Texture Library. That is, you could replace your V2 Object Library and Texture Library folders with aliases to their V3 counterparts. Make sure that the name is exact, e.g., Object Library rather than Object Library alias.