I've just managed to have [plugin~] compile with LADSPA support on OS X by trying to figure out the correct flags from other externals and hacking automake. I asked on the userlist some weeks ago but got no answer so I had to do it myself.
Right now all automake files are in a mess but atleast it compiles and it's possible to load the external and use it without problem. If anybody else needs this mess I'll gladly share it :)
I'd love to see a working plugin~ ship with the OS X distributions of pd If nobody else wants to do it I'll try to fixup the makefiles so that it should work for most architectures.
/z