UPDATE: I've made a small demo on playing video as live wallpaper, please see this gif:
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In this gif, you may note that the movie is actually playing as a wallpaper. So, that's what you want! :)
Original Bid:
Hi, nice to meet you! I'm a seasoned OS X developer who has published many apps to Mac App Store. Here's a short list of my published apps:
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As for your requirement, I'm quite familiar with IAP(In App Purchase) and other frameworks that can give you a `free-trial then subscribe` way. As for playing video, there's a trick to implement this (put a no border no title window above desktop wallpaper and below desktop icons), so I'm pretty confident in implementing your project. Please contact me for more detail.