Kudos to @ashley for pointing this out to me.
- https://www.mediawiki.org/w/index.php?title=Extension:OfflineImportLexicon&oldid=622068 (by author) - MIT (OK)
- https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/extensions/OfflineImportLexicon/+/97247c98edff3f35a2acea0744a2d601267c8ab0%5E%21/OfflineImportLexicon.php - CC-BY-NC-SA 3.0 (non-free!)
- https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/extensions/OfflineImportLexicon/+/master/scripts/OIL_Constants.js - "Quadruple licensed GFDL, GPL, LGPL and Creative Commons Attribution 3.0 (CC-BY-3.0)" (OK)
- https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/extensions/OfflineImportLexicon/+/master/scripts/OfflineImportLexicon.js - same quad license
- https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/extensions/OfflineImportLexicon/+/master/scripts/jquery.ezpz_tooltip.js - MIT (from some upstream, OK)
We should reach out to the author and determine whether they actually intended to license it under a non-free license (in which case it would need to be removed from Gerrit).