I would like to make a similar course (a copy of this) in Estonian for my girls to learn some geography. Is this considered stealing or can I use material in it?
I also want to announce that Estonia is now a Northern County (has been for a short amount of time) so the picture indicating Northern Countries is not correct anymore
It is not considering stealing.
You are free to see to content of the courses for your learning, and if you need to translate it to other language you are free to do it.
As long as you don’t charge for it, or try to make money out of it you are free to use everything you find in here.
In reply to your “Are there any country mapping maintainers here?”
I love that course by @azrael42, which is probably the best out there. I have considered offering to assist on it but I support several other mapping courses instead, although I have not created one.
As you can not contact Azrael via this Forum I would be tempted to ask @lien to contact them with that request, but I also agree with @mikatu’s comment.
However, I would also state in the introduction that it is a clone of his/her course and add any copyrights and exclusions that he/she has:
See the final level for media sources and copyrights.