Hi Fimbul!
Thanks for your kind words they do mean a lot to us and we appreciate it :) It's also really great to hear that you are using it for education.
On our store page we say at the bottom:
"If you are an officially recognised and registered School, Charity, University, Library etc where Construct 2 is being used you may use the standard licenses."
If you do not fall strictly into this definition (perhaps you are a private teacher) then please do email us, I'm sure we can work something out for you. We really do recognise the value of what you are doing.
In regards to the free edition, it's perfectly OK to use the free edition for each student, buying a license for each seat is not necessary as long as the games they are making do not break the terms of the license (people profit from them).
Over zealous students may hit the event limit :), if your place of work is interested in bulk purchasing of licenses then please do contact us as we can offer you some good discounts.
In regards to different language interface I have spoken to Ashley about this. At the moment it's planned, but we can't promise any dates this will be implemented. We do want some sort of language file eventually that the community can translate as they wish but again no promises on time for delivery.
I hope that answers your queries!