Can bdr only replicate one database per server?
BDR can replicate as many databases per server as you want. You must configure each database separately, that's all.

There is not (currently) any wildcard configuration to say "all databases on the current DB".

A typical configuration looks like:

Server1       Server2
DB_A     &lt;=&gt;  DB_A
DB_B     &lt;=&gt;  DB_B