Jscut is an open source browser based GCODE generator that uses SVG as an input.
Jscut seems to be the predecessor of LaserWeb by the same developer and several other contributors that is focused on controlling lasercutters but does basically the same with a more polished interface.
A WebGL browser based G-Code Simulator that takes G-Code and SVG as Input.
sources on github: https://github.com/tmpvar/gcode-simulator
in action here: http://tmpvar.com/project/gcode-simulator/