Merge #226

226: Add licence notes to index.md r=therealprof a=thejpster

After discussions with someone who had re-used material without attribution, we agreed it would be useful to make the licence terms more prominent to those reading the rendered book (as opposed to browsing the Github repo).

Co-authored-by: Jonathan 'theJPster' Pallant <[email protected]>

Author: bors[bot]

src/intro/index.md

@@ -98,3 +98,22 @@ it should be reported in [the issue tracker] of this book.
 [the issue tracker]: https://github.com/rust-embedded/book/issues/
 
 Pull requests fixing typos and adding new content are very welcome!
+
+## Re-using this material
+
+This book is distributed under the following licenses:
+
+* The code samples and free-standing Cargo projects contained within this book are licensed under the terms of both the [MIT License] and the [Apache License v2.0].
+* The written prose, pictures and diagrams contained within this book are licensed under the terms of the Creative Commons [CC-BY-SA v4.0] license.
+
+[MIT License]: https://opensource.org/licenses/MIT
+[Apache License v2.0]: http://www.apache.org/licenses/LICENSE-2.0
+[CC-BY-SA v4.0]: https://creativecommons.org/licenses/by-sa/4.0/legalcode
+
+TL;DR: If you want to use our text or images in your work, you need to:
+
+* Give the appropriate credit (i.e. mention this book on your slide, and provide a link to the relevant page)
+* Provide a link to the [CC-BY-SA v4.0] licence
+* Indicate if you have changed the material in any way, and make any changes to our material available under the same licence
+
+Also, please do let us know if you find this book useful!