VERGE is a Game Creation Engine: A progam that exists to help you make games.
It was started in 1997 by Benjamin Eirich (aka vecna) and Brian Peterson (aka Hahn) to make 16-bit style RPGs akin to the Phantasy Star and Final Fantasy series.
Since then, it's been used to make pretty much any genre of game from the Super Nintendo / Genesis era.
The current iteration of VERGE is open source under the BSD license. The repositories for it (and related projects) are as follows: