The goal I will be working towards is porting this application so that it will run against a standards-compliant database. Yes, standards is a loaded term.
We'll be looking at porting to Apache Derby, which has as its project charter the goal of being the SQL92 standards-compliant database engine for the Apache DB project.
When you write for Apache Derby, you gain almost complete upwards compatibility with DB2 (a standards-compliant and standards-setting database).
Full disclosure: I wrote a book on Apache Derby coming out in the next couple of months, and as an IBM employee DB2 pays my mortgage and puts food on my table.