Good day,
I find your project very interesting and I'd like to work with you. I'll be realistic, Google has been changing the YouTube's public interface quite a lot lately basically to prevent "leaches" which are basically applications downloading and/or scraping their website, but I am able to develop your application for the current interface of YouTube. I can develop your video download for the price mentioned in my bid, however you may need to do some occasional maintenance every once in a while when you notice a change in the YouTube's public interface.
I'll be looking forward to your reply.
Thank you.