The primary advantage they have over competitors is a trusted brand name. This name has been built, in part, by engaging and contributing to the open source community.
If GitHub were to open source _all_ of their software, some copycat sites may appear. These sites would not have a trusted name, thousands of well known open source projects backing them up and the expertise to properly run an instance of GitHub. As long as GitHub doesn't try charging users too much to use their service, there is no reason for people to use competitors to save a few dollars a month (reliability is far more important than a few dollars here and there).
Some open source projects may decide to operate their own infrastructure. However, this is highly unlikely because GitHub _as a service_ is much easier and more reliable than an independently managed instance. If GitHub can retain the open source community, they become "the hub" that everyone wants to be part of. As long as GitHub is known to support open source in a meaningful way, given the resources available, I'm sure they'd benefit from hundreds of open source projects improving upon and patching GitHub code.
I think they could quite readily open source _all_ of their software.
If Github went in that direction, they would have to sell services to Enterprise clients to maintain/deploy the client's Github installation instead of selling the software itself.
The costs of setting up a geographically redundant GitHub clone and continuously updating software and configuration are far in excess of the mere $200/month GitHub charges for their Platinum plan: unlimited users, unlimited public repositories and 125 private repositories. Even the Bronze plan for $25/month with 10 private repositories is exceptional value to businesses that only develop a few pieces of software.
At GitHub's price points, a manager would be crazy to take on the risk, expense and effort of setting up their own clone. The obvious "but..." excuses don't even apply because:
1. GitHub offers enterprise "run GitHub from your own server room" services for companies that have greater needs for confidentiality/customisability.
2. Private organisations can take their source code and other data with them. This means that users are free to move elsewhere (regardless of whether GitHub is entirely open sourced) if GitHub suddenly decides to charge $1,000/month/user.
And how many businesses really need support for geographically redundant GitHub clones with continuously updating software and configuration ?
If anything, them having this option at all makes no sense, as the real value of GitHub is in the collaboration and discovery tools it brings, useful for contributors working remotely.
Unlimited users, unlimited public repositories -- I have that on my own VPS. I just configured my own Git repository. It's a piece of cake. Even companies like Adobe get along just fine with a Wiki and a Perforce repository.
Basically when selling a product or a service, you do have to ask yourself: how big is the market for this? And I'm not seeing many companies really needing private installs of GitHub and that market is even smaller if the product would be open-source.
The primary advantage they have over competitors is a trusted brand name. This name has been built, in part, by engaging and contributing to the open source community.
If GitHub were to open source _all_ of their software, some copycat sites may appear. These sites would not have a trusted name, thousands of well known open source projects backing them up and the expertise to properly run an instance of GitHub. As long as GitHub doesn't try charging users too much to use their service, there is no reason for people to use competitors to save a few dollars a month (reliability is far more important than a few dollars here and there).
Some open source projects may decide to operate their own infrastructure. However, this is highly unlikely because GitHub _as a service_ is much easier and more reliable than an independently managed instance. If GitHub can retain the open source community, they become "the hub" that everyone wants to be part of. As long as GitHub is known to support open source in a meaningful way, given the resources available, I'm sure they'd benefit from hundreds of open source projects improving upon and patching GitHub code.
I think they could quite readily open source _all_ of their software.