The Alternate Chan Alliance is a loose coalition of imageboard built around free speech. The ACA was created as a response to the censorship of 8chan, and various other communities.
The ultimate goal of the ACA is to provide a greater amount of autonomy for users, and create a distributed and integrated federation of imageboards.
Imageboards belonging to the ACA must be law-abiding sites and have some minimum moderation standards. More information regarding the moderation standards and requirements for enrolling in the ACA can be found here