[Help] If I purchase "Age of Empires II: Definitive Edition EU Windows 10 CD Key" for my friend who lives in England, will they be able to play with me even though I'm in Australia?

So essentially, I got linked a copy of AOE2 and I'd like to buy it for my friend but the link is called "Age of Empires II: Definitive Edition EU Windows 10 CD Key" and says "Cannot be activated in Australia"

I assume this means that they will have to be in EU to enable it but then after that they can play anywhere. Is this the case? Or will they be region locked?

Thanks <3