Well, [__HE__](https://github.com/zufuliu/notepad2/graphs/contributors) is active, others not so much.
Actually its not clear what license its under, the header refers to `License.txt` and there is one in the Scintilla directory immediately above the lexers directory and a different one in the top level directory, although that again says lexilla and scintilla is under their own license. I guess the same could be done if Neil accepted it in Lexilla.
But anyway, if its not upstreamed its unlikely to get in Geany sadly.