Here is his post https://www.reddit.com/r/SS13/comments/1w1i5sg/gruntz_prototype_demonstration_of_cm13_in_the/
I played it it is PVE and it can have over 2000 enteties without the server even slowing down to be honnest. Idk if it was a stress test or something but the server didn't move.
It is a US server but connection is great even from other countries somehow.
For windows I recomend the Ahwoo loader as it's easiest to update and play https://neutrino.ahwoo.com/
For Linux he has a google doc you can open from the link on reddit.
If you like CM in SS14 or SS13 I recomend this altough it will be neither of them. It will be open to the public to mod when everything gets finished now it's a test. The feature is open to be honnest but it's here and it's playable.
Comparisons:
SS13: it has WAY better connection FPS and stability it has missing features but the core is there.
SS14: It has everything SS14 has, altough some features are not added like the janitor spray. Altough it has way more, in terms of reason to do thing like clean cook and other things as you get payed to do your job. You go to the ATM and just buy you don't have to go to anyone like cargo.
Features it has that SS14 does no: Z levels it has multiple levels. Going prone makes it so bullets don't hit you.
Forgot to mention the Tonemap ( How the fire and flare looks too bright etc) You can adjust it is customisable.