Since glitch is not possible to play on the mac users' salvation called Flash Standalone, this is as efficient as Glitch gets on a mac:
http://fluidapp.com/
Use it to create glitch.app based on "http://glitch.com/game" URL
It's free to use, just has some features unavailable in free version.
Of course, newer macs will have no problem with glitch performance and lucky owners are free to ignore the post.