HAF stands for Hive Application Framework. It's the new framework software we've developed to make it easier to create high-performance Hive-based apps.

The block explorer is being created for several reasons: 1) as a further way of testing HAF itself to look for any improvements we should make, 2) to provide a relatively light weight block explorer for API node operators (the major cost is the storage for the HAF database itself and they will already be paying that cost), and 3) to provide an open-source block explorer that is easily extensible for 2nd layer apps (2nd layer apps will likely want unique block explorer features specific to their functionality).