Here are the various ways of starting Bluefish.
1. Launching Bluefish
In GNOME, Bluefish can be started from the Applications/Programming menu. From a terminal, simply launch bluefish using the command bluefish.
Then use this command in a terminal: export LANGUAGE=fr_FR; export LANG=fr_FR; export LC_ALL=fr_FR; bluefish & if you use a bash-like shell.
For French users, if you want to get the custom menu in French language, launch it with the same command as above. If you run bluefish in GNOME, launch it with this command the first time after installation, thereafter you may launch it via the Applications/Programming menu.