Created a git repository now https://github.com/SvetlanaTkachenko/mediawiki-extension-HeadScript any issues may be reported (and/or patched!) there. I welcome the original author to join this project with push access.
Topic on Extension talk:HeadScript
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I created a pull request half a month ago. Are you actively monitoring these extension repositories?
Thanks for porting this to GitHub. It doesn't look like the original version from jingames.net
by @JinRyuuNagy: has had any updates since November 2016, but the JinGames version still works on MediaWiki 1.31.1 LTS. Nicole Sharp (talk) 07:47, 3 June 2019 (UTC)