Hello !! 
I would use EU4 to learn to develop.
I would start by making a simple demo for the oculus.
my question : then I pay 19 euro only once and continue to learn and share my demo for free?
thank you for your answers and Sorry for my bad english, I’m french ^^
Yes, you can pay once and keep everything that was available when you payed. But you don’t get new updates.
Correct. But of course you wont get any updates on the Engine itself until you renew your subscription.
Ok! thank you very much!
This should be enough to help me learn.
thank you for your quick responses 