DAL appears to have seen little use, and eventually Apple sold it to Independence Technologies in 1994, during a sell-off of a number of "high-end" packages such as their X.400 server and an SNA client.
Like Oracle's PL/SQL or Microsoft's Transact-SQL, DAL is essentially an extended version of SQL supporting basic query functionality and adding clean syntax for cursor operations, logic, and loops.
When sent a command, early versions of Apple's DAL interpreter broke down the statement and re-built it into subqueries for the underlying data sources.
This adaptor made DAL considerably less appealing than later systems like ODBC, where the translation normally takes place on the client side and is typically included for free with the database engine.
The downside to the ODBC approach is that, theoretically at least, more network bandwidth is used up to pull the "raw data" to the client machine for processing back into a standard format.
DAM was ODBC-like in concept, but did not include the SQL layers, it was strictly a system for sending "opaque" queries and receiving result sets.