My apologies I heard git and I immediately thought Linux kernel.
Git is a great example of the type of project which thrives in open
source.
1. It is a utility made *for* programmers.
2. It does not often have a direct connection to the Companies final
product(obviously it improves general quality, but it not really sold to
customers by the companies using it)
3. Everyone needs it, but no one really wants to pay for it.
4. It helps get a community when Linus started the project.
5. It is used by the Linux kernel so any company that uses the Linux
kernel uses it at least to review commit logs and most likely to sync
code.
My current favorite Open Source project is the Chromium browser. It is a
pleasure to use and rather painless considering its age. Obviously,
funded by Google and released under a dual license a GPL?(it is unclear
exacly the open source license) and propriety commercial Google
License(renamed Chrome) which I do not know off the top
of my head. Therefore, the open source community can work on Chromium
project and Google can make money of their Chrome browser. Obviously,
they also plan to have it be the "Only application" on their new
OS.(Though they will also be running some services over a DBUS
interface.)