There are many open source php community systems you could tweak to your liking, there is buttercoin git, but mostly if not all the sites use a custom built script/environment that everything is ran off of. Creating a website like cryptsy would require a knowledgeable team of programmers and a lot of hard work + time. With that being said it can be done just find the right team.
buttercoin gitOpensource Bitcoin Exchange Software
Cool, searching for a demo now.
This?https://www.buttercoin.com/#Not really what I expected.