@it33 I think the question @Tom was trying to ask was can he rebrand the UI to something other than Mattermost.
As convoluted as the project's licensing is; MIT for binary distribution, Apache 2 for some of the UI, and AGPL 3 for the bulk of the code. The simplest response to a question like this is - adhear to AGPL3 requirements. That means if you are hosting the service for anyone other than yourself and you modify it, you need to make the code available.
So in the case of a not for profit, they would be hosting on behalf of their users because they're providing a service and need to acknowledge that as per AGPL 3. But there is nothing in the licenses preventing users or organisations from sticking a different logo up.
Do you agree?