Totally fine so long as it's no more than a cost share, how that share is worked out is another thing entirely, I suspect they're allowed to pay for the fuel and the landing/handling fees etc but you'd need to ask Miles and ShyTorque about that.
You're confusing the rules with those for a pilot without a commercial license!
In circumstances where the pilot is an employee of the aircraft owner (or company), holds a commercial license and the required Class 1 medical certificate, he or she isn't required by law to share the operating costs. The operating costs may be entirely met by the aircraft owner. The pilot can be paid by the aircraft owner.
As stated above though, if anyone else on the aircraft is required to provide payment to be flown, that is where an AOC IS required. A private owner employing his own pilot/s is not required to hold an AOC.