It's basically UE4SS 3+ but with the following changes for Crime Boss:

• Changed the hook BP mods are started in the BPModLoader mod to how it was in 2.5. This is due to CB not calling UEngine::LoadMap when hosting the map.
  • This is unlikely to be fixed directly by UE4SS if anything it should be fixed by CB itself. https://github.com/UE4SS-RE/RE-UE4SS/issues/319
• Disabled the console by default to prevent performance issues.
• Changed GUI console graphics API to dx11 since opengl one is broken.

This will possibly be used as a framework for mods. Crime Boss uses iostore and therefore cannot have a mod loader like in PD3 (using just pak) as far as I understand.

https://github.com/UE4SS-RE/RE-UE4SS