fte+mvd+ezquake servers support .dll gamecode for natively compiled languages that can make sense of a C api, or you can write your own glue code.
Its not worth it of course. QuakeC is easier and less likely to crash. yay pointers.
lua sucks.
quake3 is not quake and has never used quakec. quake2 and quake3's gamecode was written in C. doom3 uses C for the bulk of its gamecode but also uses a variant of quakec for its map scripting.
yay quakec.
there's little point in supporting anything other than quakec from an engine perspective as this would alienate the engine from the rest of the community. retaining qc compat just doesn't do it justice and the new gamecode is incomplete and a little bit lame because of it.
that's not because quakec is some super language, but rather because quakec is a decent enough language that is far too well established in its niche.
if you want to program quake gamecode in C, you can go grab ktx, but that won't work in darkplaces.
if you want lua or some other language that gives syntax errors at all the wrong times then you'll have to write all the glue yourself. good luck with that. and even then you'll still be behind on capabilities. except for hash tables of course, but being forced to use those for everything is hardly an advantage.