When the Kad network checkbox is disabled (gray) but checked, that means that Kademlia support was not compiled into the app. In other words, "--enable-kad-compile" was not specified to the configure script, or "--disable-kad-compile" was specified.
Stes, did you compile aMule for yourself? If so, reconfigure it and add "--enable-kad-compile" to the configure command. Then, recompile it with "make", copy the executable into the application bundle, and it should work.