First, ensure you have ethernet connected to a switch or router. Or, if you've setup wifi using one of our guides, ensure that it's working properly.
Next, you can try to fix this by adding a DNS nameserver. Simply do that with the following command:
echo nameserver 8.8.8.8 > /etc/resolv.conf
The source code is located on GitHub here. Please submit pull requests with your code, along with tests supporting it.
If you have any bugs, please submit them there as well.
If you have any questions on how to use the library, please ask them on the Adafruit Forums as they will be answered quickly there.