Yes, opensource.posit.co is entirely open source :)

https://github.com/posit-dev/open-source-website/blob/main/c...

I believe the complete HTML version is right below the "Download PDF" button. Also I bet you could reproduce the cheatsheet using this HTML converted to markdown and some example from how other Posit (formerly RStudio) cheatsheets are made: https://github.com/rstudio/cheatsheets/tree/main/html