mediawiki.jqueryMsg can not handle external links with dollar signs in the URL. However, those are valid. See bug T2188 and https://en.wikipedia.org/wiki/MediaWiki:Version-entrypoints-articlepath .
External links are defined as:
sequence(openExtlink, nonWhitespaceExpression, whitespace, expression, closeExtlink)
So the URL must go in nonWhitespaceExpression. That in turn is:
choice(template, link, extLinkParam, extlink, replacement, literalWithoutSpace)
This seems overly broad, since I don't think we allow nested external links... However, the one that should match is literalWithoutSpace.
That is nOrMore( 1, escapedOrLiteralWithoutSpace )
escapedOrLiteralWithoutSpace is:
choice(escapedLiteral, regularLiteralWithoutSpace)
So I think the root problem is regularLiteralWithoutSpace, which is:
makeRegexParser(/^[^{}\[\]$\s]/);
I think this should allow $, which means removing it from the negative character class.
See Also: T49395: jqueryMsg can not parse wikilink with parameters in page name