Question: What are all the knowledge management features of Facebook's HiPal data analytics tool, and how does it work? Is it purely architectured for hadoop environment or can be used with other DBs?

Answer: 
Though this is just speculation as HiPal has not been released to the public.

HiPal is a UI for a SQL-like program called HIVE. Hive is a program that allows you to run SQL-like queries on files in a Hadoop File System. Hadoop is a distributed map/reduce architecture used for large(many terabytes) data sets. 

But as it's not open source we can't get our hands on it. But this wouldn't be used for other database systems.

<http://www.facebook.com/note.php?note_id=89508453919>
Facebook uses Hive (<http://borthakur.com/ftp/hadoopworld.pdf>) to process data. Hive is a SQL-like framework interface that runs on top of Hadoop, created by the Facebook team themselves, and latter on donated to the apache community. 

They say they analyse 20 PB of data with Hive/Hadoop.

Here is a quick start guide:
<https://cwiki.apache.org/confluence/display/Hive/GettingStarted>