FreeSCI is a free GPL'd interpreter for the old
Sierra On-Line graphic adventures based on the
SCI0 system. Those are the ones that still was based on text input but had support for the mouse and had better graphics than the
AGI style games. A few examples of games that run (more or less) well with
FreeSCI are
Leisure Suit Larry (2 and 3),
Police Quest 2,
King's Quest 4,
Hero's Quest/
Quest for Glory 1,
Codename: Iceman,
Space Quest III and others.
FreeSCI runs on various UN*X/X11 boxes and on Win32.