gistfile1.txt

 The C++ source code you download at GitHub includes source for the Unreal Editor and all the tools, so you can change anything. Documentation and many support resources are included as well.
 
####You can keep the code after cancelling a subscription :)
 
 *Do I have to worry about a billing contract or penalties for cancelling my subscription?
Your subscription payment automatically recurs, but you’re free to cancel at any time. There’s no penalty for cancellation.

When you cancel your subscription, you won’t receive access to future releases of Unreal Engine 4, however your login will remain active, and you are free to continue using the versions of Unreal Engine 4 which you obtained as a subscriber under the terms of the EULA.

*I work for a game company that doesn’t use Unreal. Am I allowed to use the Unreal Engine on my personal time?

Yes, the EULA is very liberal in this regard. It doesn’t contain a Non-Disclosure Agreement. You’re free to use, learn from, and freely discuss the Unreal Engine even if you’re developing a competing product or technology.


####Linux support underway too (you can use it today!):

*What platforms can I access under the subscription plan?
Unreal Engine 4 subscription enables you to deploy to Windows PC, Mac, iOS and Android. This is all available through the engine and tools download from this website.

If you access the source code, you'll see that there is early work on other platforms, including Oculus VR, HTML5 and Linux. You are welcome to extend and modify this code, and also build and ship games for these platforms.

Therefore, if you have programming resources you can use UE4 to ship games for Oculus, web browsers, Steambox and anywhere else UE4 might take you in the future.