Support for Oracle under Linux is relatively simple, and works extremely well - as long as the Application Server architecture is a supported Oracle architecture (Wintel/AIX/HP-UX or Solaris).
From 8.92 (I think) - JD Edwards will be officially supporting Linux as an Application Server. 8.92 is the current service pack. Although "officially" JDE will support Linux as a database server in Service Pack 4 - the drivers for OCI should be bundled in the current service pack (unless they really mucked it up !) - I haven't had a chance to look at the application server code yet, but as long as JDBOCI is bundled, then it will support OCI with no issues.
Running Oracle on Linux doesn't give many benefits, except for a lower cost with regards to hardware. The closed-source versions of unix work with Oracle very well, and will usually outscale linux to some degree. However, Linux oracle IS more reliable that Windows Oracle - and the cost for the OS licenses is substantially less.
However, the performance of Linux as a Java Server is substantially higher than any of the other solutions - including Windows - up to a factor of 5 times faster ! But you'll all just have to wait until Quest Global to hear about that...!
I am looking forward to running tests with the Application Server code running under Linux. Although Redhat is the "official" supported release, I also expect different flavours of Linux to also provide different levels of performance.