Nat Friedman making the announcement on the GitHub Blog:
We’re happy to announce we’re making private repositories with unlimited collaborators available to all GitHub accounts. All of the core GitHub features are now free for everyone.
Until now, if your organization wanted to use GitHub for private development, you had to subscribe to one of our paid plans. But every developer on earth should have access to GitHub. Price shouldn’t be a barrier.
He further adds…
We’re also reducing the price of our paid Team plan from $9 per user/month to $4 per user/month, effective immediately. Existing customers will have their bills automatically reduced going forward.