Writing licensing agreements is something your lawyer should do. Your lawyer will also explain what is legally required for you to transmit the license.

Whatever you decide on, a digital receipt or digital contract is legally binding in all the world that matters, equally binding as a paper equivalent.

Personally, if I purchased a thing electronically I expect an electronic license sent to me immediately, likely through email along with a web page I can print with the receipt. Most things licensed this way come with a digital key or similar, but if your situation is more like "print this receipt for your records" then an email and web page may be all that is expected, along with your own internal record-keeping.

Writing licensing agreements is something your lawyer should do. Your lawyer will also explain what is legally required for you to transmit the license.

Whatever you decide on, a digital receipt or digital contract is legally binding in all the world that matters, equally binding as a paper equivalent.

Personally, if I purchased a thing electronically I expect an electronic license sent to me immediately, likely through email along with a web page I can print with the receipt. Most things licensed this way come with a digital key or similar, but if your situation is more like "print this receipt for your records" then an email and web page may be all that is expected, along with your own internal record-keeping.

What Frob said is right. I would also add that a good idea is to go pay for a service that does the same thing you want to do and see what they do. Pick a service that would actually have the budget to hire a lawyer and do it right. There are some antivirus programs that would qualify but try to pick something in the same field as you. creative commons publishes some license that might work for you.