Developer website: SilverCreator
SilverCreator is a new card-based game and application development system from SilverNetworks! SilverCreator lets you express your ideas quickly, easily, and freely. You can even sell your programs, because there's no royalties. Sprites, movies, sound, and more let you create a multimedia rich game. Scripting, Methods and functions let you create a modern game easily. 2-player ONLINE games are easy, with built-in game socket support. And with click-areas and keyboard support, there's so much more.
Version 1.5's incredibly complete release notes are available here.
Mac OS X 10.1.5 or later