MIT License
The short permissive license from MIT, a couple of paragraphs that are now the most common open source license there is.
The text took shape at MIT in the 1980s, partly for the X Window System, which is why it circulates under names like "X11" and "Expat". Its core is one sentence granting the right to use, copy, modify, sell and sublicense, one condition that the copyright notice be kept, and an all-caps disclaimer that the software comes with no warranty whatsoever.
Brevity is the selling point: a lawyer can read it in a minute. React, Node.js and Rails use it. React moved there in 2017 from a BSD license with a home-made patent clause, after the Apache Software Foundation banned that combination from its projects. What the MIT License says nothing about is patents, which is why larger projects tend to reach for Apache 2.0 instead.