I'm looking for an open source media player and I've come across flow player. It is licensed under the GPL, but also requires their branding remain visible on the player. This seems ridiculous, but they claim its compatible:
http://flowplayer.org/download/free-license-faq.html
If this were actually valid under the GPL, couldn't tons of companies release GPL software that has branding requirements so severe that no one would actually use the open source version of the software?
They can't require that the branding remain visible, unless said branding contains visible copyright notices. Even then, as long as the copyright notices aren't removed, they could be relocated to where you'd put your own copyright notices, and the branding removed.
The whole point of the GPL is to give people the freedom to use and modify the app as they please, as long as others have that same freedom. The requirement that it look the same violates that freedom, and is incompatible with the spirit (and probably the letter) of the license.
Now, they can require that your app not pretend to be the original, and they can require that you clearly identify them as the author of the original code. But they can't mandate that you do it a certain way, other than by changing the name, logos, etc to something else, retaining all copyright comments in the code itself, and displaying an appropriate copyright notice in the usual place in your app.
Disclaimers: IANAL. YMMV.
I think you're reading it wrong. It seems to be saying that the copyright notice must remain visible, and that you must remove their branding and change the name if you distribute a modified version. This is a common and valid requirement for open source software.
Licensees that do modify the Program, taking advantage of the open-source license, may not use the Flowplayer mark or Flowplayer logos and must change the fullscreen notic (and the non-fullscreen notice, if that option is enabled), the copyright notice in the dialog box, and the notice on the Canvas as follows
The only thing even a little suspect is that they specify where exactly the copyright notices should appear. This obviously makes little sense, since you could modify the program such that those dialogs and menus no longer exist.
A key point here is that Flowplayer is the owner of the Copyright.
If you don't think the license they're granting you (GPLv3 + their additional restrictions) is a valid license, then you don't have a license to use their code.
As the sole copyright owner, it is at their discretion to decide what licenses they release any code under.
(Conversely, if they were taking GPL code that someone else had written, modifying and adding additional restrictions to the license for their modified version, then I believe that would not be allowed.)