I know this was already asked a lot, but now that Unreal Engine 4 is free, (and UT has a modding tool) it is up for question again.
So: Can we make our game moddable and provide an SDK with our game (like UT does), allowing it to easily be modded?
Also, while I am already asking, what is about showing the UE4 logo on game launch? Has something changed on that subject? (I asked this question before, which was answered with “you don’t need to show it, but you can”)
Thanks in advance,
The rules regarding editor distribution are largely in the EULA sections 1(a)-(b); distributions to the general public can’t include the editor (or modified editor/tools). If you want to distribute an editor for your game for modding purposes, per 1(b) you can do that through the Marketplace or Epic’s GitHub UnrealEngine Network. Thankfully now it’s easier than ever for your customers to sign up for a Unreal Engine license so once you’re set up, they can get to modding right away.
Regarding use of the UE4 logo, the EULA doesn’t come with a trademark license. However, if you’re interested in showing the logo on game launch, you can fill out a trademark license here (upper right hand corner).
Alright, thanks for the information 
One thing im still not clear. To allow modding, do i have to release the source of my game?
That’s definitely not a legal requirement