you can't enter the device license in the image without a tool license. yes, some here on the forum will tell you it's possible to find licenses or cracks for the tools.
it could be possible for someone to build custom licensed images. it's just more of a logistical issue. you'd need to send the developer your hardware so he can work on it and debug it properly. he'd need to make sure the image has all the dependencies for what you need. then what happens if you want to make a change and you don't have the tools? you have to rely on that one person all the time to keep giving you updates. i doubt it would be free unless that person has a lot of spare time on their hands.