The STACK-demo course that ships with the question type (taken from githhub) has a link to a website that used to point to some information about Maths questions, but now links to a site offering home remedies for hemorrhoids, so next time someone is updating the repo it might be a good idea to change that. It is in the link titled HE STEM Programme.
Thank you very much Marcus,
It looks like this old project website URL has lapsed, and I've removed it from the demo course, pushed and updated version and emailed the previous project leader. I appreciate you letting me know!
I won't make many and obvious jokes about this.....
The jokes do rather write themselves . That site sounded interesting so if you get a useful reply from the previous project leader I would be interested.