# book6

This book is irrevocably open source.

For text, we apply the Creative Commons Attribution 4.0 license, known as CC BY 4.0. See [https://creativecommons.org/licenses/by/4.0/](https://creativecommons.org/licenses/by/4.0/). This is also the license used by the IETF Trust for text.

For any associated code, we preferably apply the Revised BSD License (a.k.a the BSD 3-clause license). This is also the license used by the IETF Trust for code.