The document discusses open source grid middleware packages. It describes how grid middleware lies between grid hardware and software, providing services like remote process management, storage allocation, resource allocation, and security. It then summarizes several popular open source middleware packages: BIONIC was developed for the SETI@HOME project; UNICORN provides a Java-based integrated grid computing environment; GLOBUS is a widely used toolkit developed by the Globus Alliance; and Condor-G builds a high-throughput computing environment from Condor.