With postgresql, when I try to define which builder to use, only Script is available, even if others builders are defined.

Looking at the log I saw:

net.sf.hibernate.util.JDBCExceptionReporter logExceptions ATTENTION: SQL Error: 0, SQLState: 42883
net.sf.hibernate.util.JDBCExceptionReporter logExceptions GRAVE: ERROR: function locate(character varying, character varying) does not exist

I added the two following functions to my database (not sure the second is needed)

CREATE OR REPLACE FUNCTION locate("substring" "varchar", string "varchar")
RETURNS int4 AS
'select position(lower($1) in lower($2));'
LANGUAGE 'sql' VOLATILE;
CREATE OR REPLACE FUNCTION locate("substring" "varchar", string "varchar", "position" int4)
RETURNS int4 AS
$BODY$select CASE WHEN locate($1, substring($2, $3)) = 0
THEN 0
ELSE
$3 + locate($1, substring($2, $3)) - 1
END$BODY$
LANGUAGE 'sql' VOLATILE;

and after that bamboo seems to be working just fine.