My workplace uses an open source project with an AGPL 3.0 license. It's been abandoned as far as I can tell – no commits for 5 years aside from a handful of contributed pull requests (the most recent of which was 3 years ago, by me.)
I've created a fork of the project and started rewriting large swaths of the 20 year old codebase. My primary intention is to make it more usable and reliable for my company's internal use. But the fork is public on Github so anyone could theoretically download it.
The project consists of PHP code, and the footer of every page displayed to the user contains a notice that the software is AGPL licensed, as well as a copyright notice from the original developers:
Foo 2.0 is licensed under the AGPL 3. Copyright (C) 2004-2015 - FooBar S.L.
In addition, the first page seen after logging in contains not only this notice but the full text of the AGPL 3.
My question is, do I have any obligation to leave this old copyright footer in place on each page? Would it be sufficient instead to display this information when a user first logs in? In either case, should I keep the existing wording? (I'm not sure how resilient copyright is, compared to the AGPL which I know is fairly permanent.)