The questions and source code of Integrity are licensed under the MIT Licence.
Maths is for everyone, so you’re more than welcome to use and redistribute any of the questions. That being said, if you’re using them in bulk, some credit and/or linking back to Integrity would be much appreciated!
The written content in the Integrity guides is licensed under CC BY-SA 4.0↗. Please provide credit if reusing the content and redistribute under the same licence.