Rebranding/Customizing ModX Manager appearance/theme

It seems quite easy to put your custom content in the managers’ theme like shown here and here.

I am currently wondering how far one is allowed to take this without violating the ModX GPL license:

Can anyone please shed some light on this? Am i allowed to replace all logo’s or am I only allowed to add mine? Is it sufficient to just keep the "© 2005-2010 by the MODx. MODx™ is licensed under the GPL. " at the bottom of the login page and the similar notice in the help section?

Hi,
This post might help you,

Indeed that was the kind of information i needed, specifically Ryans’ post

Thanks a bunch for digging up that thread for me!