There is no restriction, but there is also no reward. For initial distribution some sort of block generation is neccesary. Thanks for thinking with us.
It is potentially dangerous due to possibility of 51% attack. It will be safer to include restriction during next fork.Well, its a choice between running out of blocks if someone points large amount of hashing power to the network and the very little chance of an 51% attack. Next update I will add the limits to an reasonable block height. Thanks again
