Is this project in any way supported by Apple? Did they release any code to get this started?
Nope. Never word one from apple.
Check out this product as an example: http://www.thecus.com/products_over.php?cid=1&pid=1
That *is* firefly/mt-daapd. Your requirements for using this code is based on the license it is released under — the GPL (ASPL for the apple mdns responder).
You’ll want to consult your lawyer, of course.
I don’t know if they are using the same code but they openly mention iTunes support on their website. Is this legal?
So long as they comply with the terms of the licensing, I don’t see why not. I’m the only one with standing to sue, and I view it as within the license agreement. Same thing with linksys, or any of the number of others that bundle mt-daapd/firefly in their nas hardware. Now, if they modified it and refused to release the modified code, that would be another thing altogether.