I could still download it from the Play Store some months ago, and I can’t find it any more. I found no news about it on Google.
The link to the app on the Play Store appears in a Github blog post in July 2012.
EDIT: My question is off-topic, but the latest answer is here: Github seems to drop official support for the mobile app and works on the mobile web access.
Github officially use a web interface:
Update (Q1 2020): GitHub have released a new app out of beta testing. See: github.com/mobile/
You can find it here : https://github.com/forkhubs/android