Welcome.

 To keep it short - FXGAS used to be PHP framework in development (and its very early alpha is available on sourceforge.net ), but it's currently being re-developed as Drupal 5 module. What will it be for?

 Game development. FXGAS will be library and platform for browser-based games. Not for creating clones of existing games, but for allowing developers to focus on game instead on spending time re-inventing the wheel (coding things like user support, forum, navigation, theme support - things included in Drupal; AND things like creating maps, items, player and non-player characters; creating economics, marketplace etc. - which will FXGAS provide).