Thankfully, Northstar makes Titanfall 2 completely independent of EA if need be. Right now they still check the EA client ID against EA's servers to get around

Thankfully, Northstar makes Titanfall 2 completely independent of EA if need be. Right now they still check the EA client ID against EA's servers to get around copyright/legal issues, so you have to own the assets according to EA in order to play a modded private hosted version, but there is no reason the EA-check couldn't be removed. The loader is open source, so anyone who wants to could fork it and do that. I suspect, however, that this time people got lucky: the Titanfall 1 and 2 games contained most, almost all of the server-side requirements/assets, so hosting a server was mostly a matter of breaking in to one DLL file and a few game script modifications to get access to the entire source engine and game features. As far as I understand, the main missing content were the navigation meshes for the AI, a few scenario scripts, and some party/lobby features. Most, if not all of those have been reverse-engineered or created by the community, so that's not even an issue anymore. But the more games get individually specialised engines, less and less server features included in the client-side game releases, the harder it becomes to do this type of stuff. In the case of idTech, unreal engine and Source, most things outside of the main menu and settings panel are 'maps' and those are either 'hosted' by your own game client, or by a remote server. That means that due to the architecture, the client package has to have at least some server features. If games have training modes, or explore/tryout/singleplayer modes, there has got to be more server-logic/code/assets in the client package to enable that.