About a week late to post this but someone could probably use this info.
This is a community made patch to fix serious issues playing Black Ops 3 online everything from stuttering in menus to RCEs, it’s basically a requirement even if you’re just playing zombies with friends.
The latest version no longer requires you to run an exe along side the game and is officially supported on Linux now.
Are the custom maps good?
As with community generated content in any game, it’s a mixed bag. On the whole though it’s pretty good