Quote - For personal use and learning/self training, both engines are free downloads from their respective sites. You only have to buy licensing for them if you intend on selling the game you build. I'm not sure what Unity's terms are for free distribution on what you build.

Unity Pro is an add-on, that's not free.

http://unity3d.com/unity/download

 

Unreal engine follows roughly the same model, except I don't think they have a pro version for sale. The whole package is free for personal use. You can even distribute what you make with it without having to license it. If you're selling what you make then you have to buy the $99 license, and then no royalties until you've hit $20K in sales.

If you want to modify the source code, then you have to buy a license. Otherwise, most functions in it can be done with Kismet, which is UDK's node-based scripting system.

You can also build content for it and sell without licensing, since content doesn't require the actual engine.

https://www.unrealengine.com/udk/downloads/

All the details and FAQs are at those links. I'm more familiar with Unreal than I am with Unity. 

 

~Shane

 

If I used Unity or UE for machinima or a graphic novel, would that count as personal or commercial use when I am not distributing the executable code?  I have never gotten a clear answer when asking this before in other forums.  I'd like to be able to sell a graphic novel or receive revenue from Youtube, but even in the best case would not be getting anywhere near enough money to license either engine commercially.