ActiveTrade and Signal Provider commission


Would like some take on this. My signal provider is recommending I switch my brokerage a/c to ActivTrade (UK) so I can establish an Interbank a/c and they can trade directly on my a/c without me running a VPS for my MetaTrader 4 platform as I do now. But my signal provider also states and I quotE:

"We will charge 40% of your profit. It’s a broker requirement, and we have to charge this. "

I cannot get my head around the statement "it's a broker requirement",

The percentage of commission aside, as that varies, usually I think 30% on profits for a managed a/c or thereabouts, but that is not the issue. Is there something I am missing why they state it is a "broker" requirement - what has a broker got to do with setting down the law so to speak with what the provider charges me ? Know doubt the broker is getting something back , but is this the norm is such situations ?