- It means someone has obtained the UE4 source code and made changes specific to their needs
- Which source has been modified will be specified by the modifier – they obtain a specific version of UE4 to change
- Those who modified it are the only ones who can explain how, but in some way they changed the source
- Same as 3: the why is up to the modifier, but they did it because UE4 didn’t provide what they needed out-of-the-box
- Yes you can, but you shouldn’t unless you absolutely must
Check out this link (Unreal Engine on GitHub - Unreal Engine) and if all goes as it should, you can have the UE4 source code in a matter of minutes. If you ever want to do client/server development, you will need to use the engine source anyway, so it’s good to have access. You won’t need to make changes per se, it’s just that building a server requires the source code.
Just be warned that you are opening Pandora’s box.
GL!