The GitHub organization home for ALS is located
☆ ALS Prolog
Gui and TTY versions are available for modern Macintosh, Linux, and Windows systems.
The initial release of the open source ALS Prolog can be characterized as a "minimal viable open source prolog". It is a 32-bit system, and provides most everything expected in a prolog TTY shell. The Gui shell is based on Tcl/Tk, and provides a basic core, including a console and visual editor windows supporting source trace debugging. A partially complete project-oriented subsystem is present; several repository Issues indicate directions for its completion.