See this to learn what OpenJDK is about, and the ecosystem around it (including Oracle)
http://www.redhat.com/summit/2012/pdf/2012-DevDay-OpenJDK-Bhole.pdf

IBM Joins OpenJDK
http://www.sutor.com/c/2010/10/ibm-joins-the-openjdk-community/

SAP joins OpenJDK
http://scn.sap.com/community/open-source/blog/2011/07/14/sap-joins-openjdk

Twitter joins OpenJDK
https://blog.twitter.com/2011/twitter-open-source-and-jvm

AMD and Oracle team up for Java GPU acceleration
http://www.eweek.com/developer/amd-oracle-team-for-openjdk-sumatra-java-gpu-project/

Apple and Oracle announce OpenJDK for Mac OS X
http://www.apple.com/pr/library/2010/11/12Oracle-and-Apple-Announce-OpenJDK-Project-for-Mac-OS-X.html

Oracle makes OpenJDK the Java7 reference implementaiton
http://www.infoq.com/news/2011/06/openjdk-bylaws

Oracle open sources JavaFX 2.0 as OpenJFX under GPL license
http://openjdk.java.net/projects/openjfx/

Oracle open sources JavaFX 2.0 for iOS and Android
http://www.infoq.com/news/2013/02/javafx-ios-android

Oracle releases Nashorn, the next'generation Javascript engine for the
Java VM in Java8 and OpenJDK 8
http://www.dzone.com/links/all_about_oracle_nashorn_the_nextgeneration_javas.html

OpenJDK 8, Java 8 Reference Implementation
https://jdk8.java.net/java-se-8-ri/

"JDK 8 was developed collaboratively in the OpenJDK Community..."
http://www.oracle.com/us/corporate/press/2172618