What is "beerware"

n. (context computing often humorous English) software that can be used under a relaxed licence, with the user encouraged to pay for the software by donating to its author enough money to buy a beer.

Beerware is a somewhat tongue-in-cheek term for software released under a very relaxed license (beerware licensed software). It provides the end user with the right to use a particular program (or do anything else with the source code).