There is a configuration property in OWB for switching between ANSI SQL code generation and Oracle SQL. It is under the ‘Code generation options’ in the mapping configuration. The join condition is expressed in Oracle SQL join syntax and OWB will reinterpret if generating ANSI SQL.
You can change the value to false, generate the code and inspect it inline within the mapping editor;
The 11gR2 release of OWB has changes in the join component to allow you to express the join type in a logical manner, so you can indicate outer join on a group for example.