One of Them has been created using a custom build of the dim3 engine from Klink! Software. The engine has been compiled for x86_64 however it uses OpenGL. Furthermore it relies on libPNG and libMPG both of which have been integrated into dim3 using i386 APIs.
As of macOS 10.14, OpenGL and OpenCL will be depreciated, and i386 will no longer be supported. As the dim3 engine is no longer under active development, it's sadly not worthwhile modernising it. Therefore One of Them will be ported to Unity and built using the Metal API (see below).
A proof-of-concept playable demo is now available for macOS 10.13. If you'd like to try it out, or collaborate on the project, or give me a job, get in touch with me
First look at the Unity port: