Copyright on a forked GPL project?

Question

I'm working on a fork of a project under the GPL that hasn't been maintained for over a year. How do I handle the copyright notice?

Here is the copyright notice how do I add my copyright?

Copyright © 2013–2014 Philipp Emanuel Weidmann (pew@worldwidemann.com)

Final Term is free software: you c...

I have made a lot of changes and have many new features planed, I'm estimating around 60% of the code base will be different/new.

Answer 1

As long as the tiniest bit of code remains from the original maintainers, you must keep their copyright intact, but you may add your own on a separate line, like so:

Copyright © 2013–2014 Philipp Emanuel Weidmann (pew@worldwidemann.com)
Copyright © 2015 RedHatter (redhatter@example.com)

Final Term is free software: you c...