Servo would be more compelling for use with commercial software if had MIT or Apache license. The MPL isn't as bad as GPL but still isn't as generous to the developer as MIT or Apache. With the right license, Servo would be a slam dunk for replacing CEF in commercial software that prohibits reversing or tampering.
The license isn't really up for negotiation, but I'm curious what you think there is to gain with more liberal licensing? All the competing engines are either equivalently or more restrictively licensed, no?