Hello fairplay,
I see you have snuck into the forums again! I will have to talk to the mods.
I love your probing, insightful posts meant to reveal to the world what a righteous and brave soul you are - and you feature an impressive link as if to add weight to your quarrel. Let's see how we go ...
Firstly there are no legal hurdles so forget trying to wrap your post in a blanket of self-serving terms.
[1] Many people are aware, but apparently not you, that when a signature is changed in vBulletin, it changes all posts retrospectively. You have uncovered a dastardly plot - good for you! How do people differentiate? Does it matter? It's still me

and I choose not to hide behind an alias.
[2] The Lone Mamber and Absalom - what a pair. Two blokes trying to impress the world with how clever they are, twisting words and rallying the mob to their own cause. These guys write to hear the sound of their own voice, however the Lone Mamber's writing, albeit fictional, has always been funny and well written and I quite enjoy it. Absalom can't string a sentence together and has no ability to define or construct logic, but tries so desperately to sound intelligent it almost leaks out of his writing.
But to your question: The license violation so 'uncovered' by our sneaky in-depth reporter Absalom is in fact no violation at all. Absalom referred to the requirement of the author of the background image being given credit on the Mambo Love site. It is in the CSS file that refers to it. Hmm, strike two for you ...
[3] How can forum users be banned? Well it has nothing to do with legalities: it's our forum, we run it as we see fit. The forum is here for people to talk about Mambo and create a useful resource for Mambo users. We have a set of rules that - hey, did you know the ex-dev team created those rules? - must be followed. If a user is badgering, abusive, telling lies, attempting to subvert the Mambo community (or indeed breaking any of the rules) they will warned or immediately booted depending on the severity or frequency of their transgression, at the moderators discretion. Additionally, some people appeal the ban and sometimes it gets lifted. Everyone has a bad day now and then.
Strike three. There is no conspiracy.