I'd be more interested in Cobol than ActionScript, but yeah both are probably niches in 2018.
@b4n, Cobol at least would seem to be still alive, see #2021
And anyway whats wrong with ctags using a different regex library, its something we link to, and its a dynamic dll, not as if its anything inside Geany itself. Hell, its probably already in memory for most Linuxen.