Lassie is a good engine for web based games, but you can't use in commercial games.
There are another engine, but there is very old, and the gui is a old SCUMM style like Maniac Masion, DOTT or MI1 & 2, this engine is IndyJava, not is bad, support multiplayer, alpha channels, several graphics formats and has a easy scripting language, but is old and I'm not sure if it's discontinued.