olgerdovich
olgerdovich@yandex.ru
Yes, it is.
This option is described on pages 83-86 of the manual FF8.1.0 full manual.pdf from "Download most recent Firefly documentation" hyperreference of the "manuals" page http://classic.chem.msu.su/gran/gamess/manuals.html
Manual claims that semi-empirical methods are available in MNDO, AM1, PM3 and RM1 implementations and are turned on with basis choice: "Using a semi‐empirical method in Firefly is extremely simple. All one needs to do is specify GBASIS=MNDO, AM1, PM3, or RM1 in the $BASIS group."