Ok here is a simple windows-only UI tool that searches for all files of your specified type in a folder, prepends the text you desire to the top (your license text), and copies the result to another directory (avoiding potential overwrite problems). It's also free. Required .Net 4.0.
I am actually the author, so feel free to request fixes or new features... no promises on delivery schedule though. ;)
more info: License Header tool at Amazify.com
