WordPress MU

I need to install wordpress mu at the company that I work and I need to know if I develop my own theme and I include comercial adverts do I have to pay some money to someone??

what I need to mantain on the web site to not violate the GLP license?

thanks!

Yes, you have to pay money to me. All monies go to me.

No. Running ads on your site is not a violation of anything.

thanks!
Do I need to keep at the footer the "wordpress name" or something else like link that has reference to wordpress?

what if I use WP MU for the comercial purpose of the company and I don´t put any reference to wordpress?

there is someone or something "official" that says that there's not problem?
thanks again!!

Yes, you can do all that. The GPL license in the download says so.

You can go through and do a find/replace to change every single place it says "wordpress" to "Awesome MultiSite (Site Not Blog) GPL OpenSource CMS of Doom" if you want.