Does anyone know how to download it?
Unless there's someone who still has the game on their device from 10 years ago (if it was released) and they uploaded it somewhere, I would assume that it could be found and preserved here. If someone can get in tough with him on Patreon and ask about it maybe they could get him to upload the art assets he created for the game, at least? You could also get in touch with the 2 companies mentioned in the video, OpenFeint and Meuf Telecom to see about the status of the game.
Edit: Just looked the companies up, OpenFeint was a social media platform discontinued in 2012. Meuf Telecom was a gaming league(?):
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that also has this video in French (translation would be appreciated):
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All other links lead to a dead end :/
Seems our best route is contacting David himself.