There are a couple of issues that I think are at play here:
- There is no "org.richfaces" module within wildfly, so that is probably something that was created specifically for your application at your company. There is a feature request to have this added, but it never was:
- The module that is defined in the link above has nothing that adds support for TIFF images, so the module you are using is either not that one, or is a modified version of it.
- TIFF images weren't supported through ImageIO until Java 9. Prior to that, the only Sun/Oracle libraries that supported TIFF through ImageIO was Java Advanced Imagery ImageIO (JAI-ImageIO). This is quite old, and Oracle has retired it. It can now be obtained from github.
- The classloader for your war should be isolated from your separate jar deployment, unless the jar adds a specific dependency on the war. I'm not sure why your jar would see it, unless the newly-registered TIFF handler becomes visible to everybody in the VM.
So, my *guess* is that the richfaces module that your war is dependent on contains JAI-ImageIO somewhere within it, and that your jar is dependent on the war. If you can, I suggest upgrading to Java 9 (or later) so that you'll get support for TIFF images directly. Otherwise, you can download JAI-ImageIO, create a module for it, and make your jar dependent on the module.