What licence should I give buyers of my digital product?
Updated
The buyer is buying permission
Give buyers a plain written licence that says what they may do with the file. The usual three levels are personal use, commercial use, and extended or resale rights. You keep the copyright; the buyer is buying permission. Price commercial use higher, and put the wording inside the download.
Saying which uses are allowed, in plain words, prevents almost every argument that follows.
The three usual levels
Personal use: for themselves only. Commercial use: they may use it in work they are paid for. Extended or resale: they may include it in products they sell.
Price them differently. Commercial use is worth a multiple of personal use to a business buyer.
Write it in everyday language
Two short lists: what you may do, what you may not. Nobody reads a page of legal text on a product page.
Put the same wording inside the download so the buyer still has it a year later.
Say what happens with credit
State whether attribution is required. Vagueness leads to buyers guessing, usually in their own favour.
If you do not require credit, say so. It removes a hesitation before purchase.