Board Thread:Support Requests - Getting Technical/@comment-24789339-20140612024826/@comment-856287-20140613064026

I'm not sure you can stop it from being added; appears to be happening in the MediaWiki code. ...at least I guess so.

You can change what it says though. It's either MediaWiki:License-header or MediaWiki:License. I'm not sure which one is right... you'd have to experiment and find out.