MCP certainly is still active, and I believe 1.41 is the current version.
Admittedly I'm still using 1.38 here, but I've been too slack-arsed to install 1.41 yet

My current MCP 1.38 setup runs perfectly under OS 3.9.
It takes quite a lot of work setting it up, as often it's not obvious what MCP functions and patches will interfere with other things you might be using. Things like ReqAttack can be a problem if you don't have MCP set up just right.
Once it's all working correctly, it's very rewarding, as MCP allows a high degree of system flexibility.
My advice in setting up would be just to enable a few things at a time and test it works, rather than enable a big bunch of MCP features and then try to figure out which one is causing the problem.