Gunman Contracts started out as a HL:A mod, it just released.

Boneworks had a homemade engine called Marrow I think, so I assume Bonelab is too? I just looked it up:

The 1Marrow Interaction Engine (or just the Marrow Engine), is a proprietary physics framework developed by Stress Level Zero for the Unity engine. Originating from BONEWORKS’ mechanics, it contains all physics, solvers and logic used to create physics-based VR games such as BONELAB.