Generally the purchase of a Keyboard Maestro license is minutes, though risk analysis issues can affect that on occasion.
A personal or corporate license is the same. Keyboard Maestro is licensed on a per-user basis (or optionally a license can be used on a per-Mac basis).
You will not be able to include Keyboard Maestro license, it can only be generated by me or FastSpring, and I don't deal with resellers (any resellers, sorry).
You could buy the license yourself, but then giving access to the license to another entity would be problematic since you don't have that right, and you couldn't control how the license was used.
So basically, they would need to buy the license to Keyboard Maestro.
Of course, since Keyboard Maestro has a free trial, it could be set up for them to see before they need to commit to buying the Keyboard Maestro license.
Note also that there are no technical protections for a macro installed within Keyboard Maestro, and so your only protection would be a legal claim of copyright on the macro, and I'm not sure such a copyright has ever even been tested in law anywhere.