You can just send Epic an e-mail.
It’s stated that this is still an early adopter version ("The current release is aimed at early adopters, and it has some rough areas:"), also it isn’t just autodesk. Epic donated 10k$ to get better blender fbx support and workflow with ue4.
There aren’t any dlc’s, on the marketplace you have a lot of free content, and also paid content from other companies. An engine isn’t content. An engine is a set of tools, to use content and to (depends) make it.
Also, unreal engine isn’t a game, it’s a tool to create games.