Shell commands to launch Firefox Beta, Firefox Developer Edition and Firefox Nightly.
# Open Firefox or Firefox Beta
/Applications/Firefox.app/Contents/MacOS/firefox -no-remote -p beta-default
# Open Firefox Developer Edition
/Applications/FirefoxDeveloperEdition.app/Contents/MacOS/firefox -no-remote -p dev-edition-default
# Open Firefox Nightly
/Applications/FirefoxNightly.app/Contents/MacOS/firefox -no-remote -p nightly-edition-default