Well, even though C2 is not open source unless Tom and Ashley have included some hidden way to shut off all of our use of the engine then even if they go under you still have your version and license to continue producing games using that engine and as long as HTML5 is an accepted game format somewhere you will still be able to publish your games.
That is why I am not personally keen on a C3 subscription model that could be shut down and you could lose your assets if you rely on cloud storage.
I understand it will work without a cloud connection but how limited will that be?
I want to own the engine and know that engine will still work in case the business goes defunct.
Not that I foresee that happening with Scirra but it could and businesses do shut down and stop producing updates for old engines. 001 Game Maker is an example. Great engine that lost support when they went to a subscription model and stopped supporting old versions and doing updates. Got too expensive.