GNU Prolog is a free Prolog compiler with constraint solving over finite domains. GNU Prolog accepts Prolog+constraint programs and produces native binaries.
KLogo-Turtle is an interpreter of the LOGO language for KDE desktops. The KLogo-Turtle is a useful tool for teaching geometry and the basic principles of the programming of computer.
lafontaine is a graphical logo interpreter made for educational use.
Logo++ is an interpreter for drawing graphical figures following very simple instructions. Though it lacks many essential features of programming languages, it remains a funny start for beginners in computer programming, particularly for kids.
SWI-Prolog offers a comprehensive Free Software Prolog environment, licensed under the Lesser GNU Public License. The full development environment, including graphics, libraries and many interface packages requires approx. 27MB harddisk. The non-graphical kernel is about 750 Kbytes, the graphics library adds about 1.2 MB to the image. Compiled Prolog however is compact, allowing complicated programs to fit (compressed) on a 1.44 MB floppy. The kernel can be in a shared object (.so, .DLL).
YAP is a high-performance Prolog compiler. ts Prolog engine is based in the WAM (Warren Abstract Machine), with several optimizations for better performance. YAP follows the Edinburgh tradition, and is largely compatible with DEC-10 Prolog, Quintus Prolog, and especially with C-Prolog.