FYI, Astra SDK v0.5.0 is out and we have significantly improved the OS X packaging process. In particular, we did as @wouter suggested and packaged libusb (and sfml) so there are no external dependencies. You should be able to download the OS X v0.5.0 package and run the samples directly, as well as build the samples by running the samples/build_samples.sh script to build the samples without installing any external dependencies except CMake.
Thanks for your input!