Is there a way to enable static linking, at least for some libraries? It
doesn't matter much that the gem .so becomes bigger, as long as it's not
so much bigger, and that it's easier to carry around.

On the platform in question, OSX, freetype and FTGL are statically linked. Quicktime and OpenGL are defaults in every OSX install. We have incorporated code like GLEW and the model loader directly into the source tree.

There is nothing to install for GEM on OSX beyond having a working Pd and dropping the Gem.pd_darwin in the extra folder.