PGXN

Isok, otherwise known as pg_isok, is licensed under the GNU Affero General Public License version 3 (AGPL 3.0+), or (at your option) any later version, with the exception of all sample program code, sample commands, and sample configuration file components contained in the documentation, whether explicitly labeled as an example or not. These samples of program code, commands, and configuration file components are licensed under the CC0 1.0 Universal license.

The deed for the CC0 1.0 Universal license explains the license in plain language. The deed is reproduced in Appendix I. The No Copyright section captures the essence.