Construct stays free and you can still simply download a full-featured version, but you can't compile to any platform with the free version. You could test the runtime just fine, but you can't compile it. If you buy a license, you'd get a couple of new buttons that'd allow you to compile for the PC, Mac, X360, etc. Heck, I'd drop a couple hundred bucks on it if I could deploy to more platforms. It'd be a win/win.
I guess a business model like that could be attractive for most users. You could still learn the app and only if you're going to deploy your game, you'll have to pay for it - it's a fair deal.
Personally thats what I'd like to see.
Although, I doubt that it will happen.