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These are all community-contributed. You can view all the JSON source files here: https://github.com/duckduckgo/zeroclickinfo-goodies/tree/mas...

and you can search for Cheat Sheets (and all other Instant Answers) here: https://duck.co/ia?q=cheat+sheet

I believe all of DDG's 'instant answer' systems are community created and maintained... https://duck.co/ia

This is a great question. DDG is open source, so someone should be able to figure that out.

EDIT: based on other answers, this is unnecessary. These are community contributions. Pretty cool!