Well - since this is a test
I think you should try using sqlODBC - I'll be extremely interested in discovering how well it works - though I haven't much of a clue how you're going to configure the middleware - since JDBODBC.DLL isn't compiled for the unix platform !
The method which would certainly work would be using JDBNet. This middleware passes the SQL Statements between the OneWorld servers prior to reaching the database layer - ie at the JDB level (the layer between the application and the JDE Database Middleware). These messages are passed using JDENet - and require OneWorld services running on the Database Server as well.
However, as you can imagine, this is a tricky setup. First of all, you'll find that there is plainly too much overhead with "double SQL" requests - for every SQL statement created by the code, 2 SQL Statements traverse the "network". I am pretty positive, however, that you'll discover that JDENet will cache relatively well - and it will certainly be interesting to see how everything works.
Secondly, ensure that all business functions are also mapped to the SQL Server box - you should test both without the business functions mapped, as well as with the functions mapped - but I believe I remember having to map business functions when last I tried this.
You'll learn a lot about how JDB operates with this exercise. Heres another test if you find you have time - try running the JAS server under Websphere 5 for Linux !