I agree with
Rayek on this one!
That paid subscription model - quite on the contrary guarantees that one day you will no longer be able to open your game project. History has shown us many times - users being left out to dry
It does not in any way help your project or you. It's there simply to lock you on continued payment, regardless if you actually make money from the game engine or not or need to update it for new features.
I would be ok if the rent payments were so that the engine gets new features. But they really aren't - the developer can then continue charging you simply for using the software. Once they have enough users locked to that model, they will no longer worry about meeting any feature requests - as pressure on their side to improve the software so people buy the update is gone.
One day when they decide to drop support for the software, even if you want to pay rent- you will be locked out of the house - with all of your stuff still in it.
If Scirra goes away, and Chrome makes an update that breaks all your C2 games, how far up the creek will you be?