I just noticed that if you back the above URL down to the parent dir, you'll see the rest of the files and in the README they mention that the connection is via the hand-controller, so that sure sounds architecturally similar to the Celestron way.
Not that there is any apparent/implied/obvious/known-to-be-a-fact past shared history between the companies.
Haha.
I spoke to PlaneWave about this. Apparently many years ago, they used a Celestron interface, but they no longer use it and the current product / driver isn't compatible with it.
I do have the command set documentation and posted it on a new thread.