PhoneGap was originally developed by Nitobi, a company acquired by Adobe in 2011. After it was acquired, Nitobi donated the PhoneGap code base to the Apache Software Foundation (ASF) under the project name Cordova, which is the name of the street in Vancouver where Nitobi's offices were located and where the company created the first version of the framework.
One of biggest advantages of moving the code base to the ASF is that big organizations can easily contribute to the project (many companies are not only comfortable with the Apache organization and license, but already have a Contributor License Agreement with Apache); furthermore, the project is now under an open and transparent governance: its community!
PhoneGap is a free and open licensed distribution of Apache Cordova. Picture Cordova to be the engine upon which PhoneGap and its related services (debug, emulate and build services) are built. For existing PhoneGap developers nothing has changed; but for those who are interested in contributing to the project, Apache Cordova is a great chance to join a vibrant open source community.
Adobe continues to play a major role in the project, investing in its ongoing development, and the company decided to keep the PhoneGap name to describe its own distribution of the Cordova project. Other contributors to the Apache Cordova project includes Google, RIM, Microsoft, IBM, Nokia, Intel, and Hewlett-Packard.