Well to add some insight on ODWEK and CMOD Server.
What Norbert is talking about is only 1-2 method in the WHOLE ODWEK Java APIs, the xmlparse() method.
And yes, this one needs to be ODWEK Version = CMOD Version
Maybe the new API to archive documents in CMOD (which appeared in V9.5) ODServer.*load*(), then maybe, you need like the same version of the APIs
But for the "client" part of the ODWEK Java API, which is basically the 99% of the APIs, the advice is ODWEK Version >= CMOD Server.
I had never any problems with any of my past customers... It was mainly, searching, retrieving. That's it. And if that's the case, then you should not have any problems.
The only problem, which is NOT a real problem is when you want to use old ODWEK with a new server, then the new functionality are not available.
But that's exactly the same as the Windows Client. If it is older than the server version, you can still access it, but not all functionality will be available.
And depending on your setup, and migration path, it might be a must to have for a few days/weeks/month (I hope not years), that ODWEK Version < CMOD Server Version OR ODWEK Version > CMOD Server Version.
The advice I had from the IBM Labs (ODWEK main developer) was to always use the latest ODWEK Java API to develop and reach the CMOD Server even if the version was 1 main version difference.
That advice was several years ago, before V10.1.
Maybe today with the integration with some of the functionality of the server part, then it might not all be always true for all part of the API (like save documents or xml work).