I understood that this component was build for Async Model of uServices.

However, PLENTY of legacy Domain Specific DB Source are already on RDMS.
These DBs are: Oracle/DB2/MSSQL/SAP/...

Existing DB can be easily exposed by DBA via view, and can be accessed by Hibernate.

Since Hibernate has a LONG GOOD list of HQL/SQL Dialect support, why not consider a quick building of connect-service using the latest Hibernate?
https://docs.jboss.org/hibernate/orm/5.2/javadocs/org/hibernate/dialect/package-summary.html

Or in worse case, IF HQL cannot do connector well, you may consider using:
https://docs.jboss.org/hibernate/orm/3.3/reference/en/html/querysql.html