JUG is a set of Java classes for generating UUIDs. It generates UUIDs according to the UUID specification (IETF draft), found (for example) at:
http://www1.ics.uci.edu/~ejw/authoring/uuid-guid/draft-leach-uuids-guids-01.txt
or at Wikipedia (draft id being "<draft-leach-uuids-guids-01.txt>")
Alternatively you can also read newer IETF draft that describes URN name space for UUIDs, and also contains UUID definition.
JUG was written by Tatu Saloranta (tatu.saloranta@iki.fi) in 2002 (or so?), and has been updated over years. In addition, many other individuals have helped fix bugs and implement new features: please see CREDITS for the complete list.
Jug licensing is explained in file LICENSE; basically you have a choice of one of 2 common Open Source licenses (when downloading source package) -- Apache License 2.0 or GNU LGPL 2.1 -- and you will need to accept terms for one of the license. Please read LICENSE to understand requirements of the license you choose.
JUG can be used as a command-line tool (via class 'com.fasterxml.uuid.Jug`), or as a pluggable component. Maven coordinates are:
<dependency>
<groupId>com.fasterxml.uuid</groupId>
<artifactId>java-uuid-generator</artifactId>
<version>3.1.3</version>
</dependency>