Originally Posted by vpJane
I mean, really, just go to the sources and ask. Some of the people here who will tell you it's illegal are not lawyers or employees of the companies that MIGHT grant you permission if you ask.
It's illegal if you are copying a copyrighted work AND you do not have permission from the copyright owner. If the work is public domain or you have permission, you should be OK.
You can contact the makers of Angry Birds here:
Read the last post on this other thread, by ANDaniels, for an example.
In that example, permission was granted by the person managing the company's Facebook site. To be safe you should really have permission come from the legal department or someone you can verify actually has the authority to grant permission.