Re: TOTALLY CONFUSED...
You shouldn't need any other packages or applications (suites), if you have successfully built AMBEserver from the source. I couldn't find default Github repo, but this one has what I remember as a working approach for building and running the app.
You can start the program from the command line to get started, all the configuration required is given as command line parameters. (As outlined in the above README.md) I believe the ambeserver-ttyUSB0.service file you referenced is just necessary to have AMBEserver auto start when the Pi boots.
I hope that helps...