In our documentation on installing Bamboo on specific databases, we do mention the following in the case of Postgres:

Please note, the JDBC driver for PostgreSQL 8.2 (PostgreSQL Driver 8.4.x) is bundled with Bamboo. You do not have to download and install the driver.

Many users assume with the above information that the JDBC is bundled in all distributions. It will be nice if we can add an additional info to that comment.