Well sounds like you got the full folder treatment I just got two loose files.
It shouldn't be hard for him to alter the code to read license1.key license2.key etc.
Failing that he should spell out clearly to end users in his delivery email that they are different. My email just said here are your licenses and I figured ok one for my home setup and one for Capt dad but surely they must be identical since they are so named and nothing is mentioned ...
I had even mentioned in my purchase email that I intended to use the plugin on my three home computers and to confirm I was good to go. That didn't trigger any elaboration on installation.
I feel He needs to provide some more detail on the install process / setup if he wants to broaden his base from it professionals to the average Joe. Your own plugin details would be a nice model to follow for clarity.
And I shared this all with him via email and of course he can also say go jump in a lake.
T