XGP 1.2.0 for Mac could be downloaded from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. XGP works fine with Mac OS X 10.6 or later. XGP-1-2-0.dmg is the most frequent filename for this app's installer.
We recommend checking the downloaded files with any free antivirus. The most popular versions of the software are 1.2 and 1.1. The bundle identifier for XGP for Mac is net.sourceforge.xgp. The actual developer of this free software for Mac is Lindsey Spratt. The application lies within Developer Tools, more precisely IDE.
From the developer:
XGP is an integrated development environment the extends gprolog to work with Cocoa under Macintosh OS X (10.6). It extends gprolog with builtins predicates for dialog, menu, and graphics facilities.
gprolog (GNU Prolog) is primarily the work of Daniel Diaz, It is a largely ISO standard-compliant Prolog, extended with constraint logic programming.
You may want to check out more software for Mac, such as wxFormBuilder, TopCoder UML Tool or Site Studio, which might be similar to XGP.