Cool! Pay me and I"ll build you a linux server with mattermost and git on it. You can self host all the things they're putting together here on keybase. And it's free now, but it won't be for too much longer, soon there'll be freemium and then a full paid service. Because they want you to build an environment and workflow around it, and once you're making money with it you'll gladly pay a bit in a few years or so when you're large enough to afford it.

But until then, I"ll totally build you a self hosted solution. I'll even work remote.