Could you do the following for me:
1. Log into Github. Edit your user profile and make sure the 'Public Email Address' is marked to a valid email address instead of 'Don't show my email address'
2. If you have the Automatic Registration setting enabled in JFBConnect, please set it to No.
3. Click the Github login button (from SCLogin module, etc).
Does the email address get populated for you? I realized the profile I was testing with had the public email address to Don't show. When I switched it, the value was pulled in.
-Melissa