May be my reply is too late and people already know this. The entire thing has two layers
1. Data layer (Hadoop -HDFS) -- SAS accesses the hdfs file system using hadoop access engine (+additional modules) to read and write files
2. Processing layer -- Depending on the modules that have been licensed SAS can leverage HADOOP nodes with SAS Embedded processes (Some procs can run in distributed fashion). Use a native hadoop call to distribute a java map reduce job to retrieve results. Use a LASR cluster on top of HDFS cluster to do in memory computation etc.

If you just get HADOOP access engine the things you could do are limited. If you get other modules such as embedded process, Data Loader, Visual Analytics Platform you could do much more.