Glass Development Kit (GDK), a development kit to develop Google Glass glassware
The Google GDK is the Glass Development Kit for Google Glass. This kit allows developers to create Glassware how they would for Android. Everything built from the GDK is written in Java or JVM languages. The GDK is an add-on to the standard Android SDK, but targets the Glass specifications and has modifications to allow developers to create cards to be displayed on Glass.
Read more at GDK Developer Website