Probably just the wording scaring you a bit. Git is simply a protocol
for sharing code. Those who are programming org-mode can work together
on all of the little files that make org-mode work. These files live
on a server, and those of use who use org-mode "pull" (or clone) from
that server. In this way, you can keep your version up to date with
what the coders are doing.
You don't have to have anything running. There's a server that keeps
all of the org-mode program living on it. We, the users, use "git" (a
small program) to interact with that server and download a fresh copy.
Git is smart, though, and after the first long download, every time
you run it afterwards, it only pulls down files that have changed so
that it's much faster afterwards.
Sound good?
John