Add Apache incubator notice to README

README.md

@@ -89,6 +89,17 @@ Please refer to the [Configuration guide](http://spark.incubator.apache.org/docs
 in the online documentation for an overview on how to configure Spark.
 
 
+## Apache Incubator Notice
+
+Apache Spark is an effort undergoing incubation at The Apache Software
+Foundation (ASF), sponsored by the Apache Incubator. Incubation is required of
+all newly accepted projects until a further review indicates that the
+infrastructure, communications, and decision making process have stabilized in
+a manner consistent with other successful ASF projects. While incubation status
+is not necessarily a reflection of the completeness or stability of the code,
+it does indicate that the project has yet to be fully endorsed by the ASF.
+
+
 ## Contributing to Spark
 
 Contributions via GitHub pull requests are gladly accepted from their original