this needs the non-profit organization to be registered in the US[1]
As far as I know, you can use a free non-profit organisation account,
but you can
move to the premium account with no charges if you are registred in the US.
One thing is to add, the user accounts given by this service are limited by
100 MB size for each. it shows its 5GB
That's for the Premium account, the free account gives you only 100
MB/user, unless
you can proof that you're a NPO in US.
no premium accounts get 25GB free accounts gets 5GB+ check this
screenshot[1] for a test account i made over there :)