Where can I read what this project seeks out to do?

I didn't understand the GitHub readme file. Other than that it seems they are midway at implementing something.

They've built emulators for many, many old computers. The website is clearer than the github page. http://simh.trailing-edge.com/

The PiDP-8/I is a PDP-8 replica built using a Raspberry Pi and simh

https://hackaday.io/project/4434-pidp-8i

(as one example for what you can do with simh)