Is a Halo 2 Vista Co-Op mod being developed?

Feb 6, 2019
Lambda Core
There's actually a forum post on here from the creator of said mod. He recently posted a link to the newest version in December of last year.
I don't believe the old version works on newer versions of Project Cartographer, so be sure to download the new version.

EDIT: I want to note that I don't believe it's in active development, nor do I think this new compatibility release actually adds new features. I think it's just a compatibility fix.