One time on an Apple mailing list for a java developer preview (aka pre-release) I let the Intel build leak in a minor and non-obvious way. There unfortunately aren't archives of this list kept by Apple, and I no longer have my copy of the message. I believe I wa explaining how to determine what libraries your library needed, or perhaps to determine if your JNI library was pre-bound. This is done with 'otool'. I usually provide options to have 'otool' give lots of data about the library being inspected. This includes its FAT header information. I provided an example in my email, and I was working on my Mac OS X Intel build machine. I copy and pasted the information into my email, and I snipped all of the Intel information. However (and memory escapes me) I had somehow left something funky in there. I believe it may be the dependent libraries are listed twice, once for each architecture