Using the Bitcoin digital currency, do I have to be a part of their cluster?

I want to be able to have a digital currency for my game community. It would be its own currency and people could buy games, in-game items, or physical items with it. They could sell these items to each other after use through our market.

So what I dont understand about Bitcoin and many other open source digital currencies is, can I do this on my own, or does the open source software make you be part of the bitcoin economy?