is it ilegal?

[Shadowxxxx]

Hello, i wondering if its legal or ilegal vb's side,
i will give you one example:
when you trying to acsses not premission page, its says vbulletin message, is it legal to change the "vbulletin" to our own forum name?

and second, copyright, i saw some forums they just deleted it, i know its to support vbulletin and they're work and all that, and they obviously want to let they're name stay on any forum,
is it possibly to remove or change it, if yes is it cost? (dont respond with ilegal forums and stuff, i saw reall legal and since 2003 forums without any copyright)
cause i saw some license huge forums without any copyrights