AFAIK, Guvnor doesn't need the classes definition to open the process. It does need it for building the full package though. So maybe you are facing a different problem here. Do you see any error message or stack-trace in the log of your application server? If you want to upload the model jar into Guvnor you have to go to "Knowledge Bases" section in the left menu and do: Create New -> Upload Pojo Model After that, you need to compile your package: click on the package -> (if you are using 5.3 version of Guvnor, you must go to "Edit" tab) -> Build Package
This is what I could find in the logs.
2011-08-24 14:42:29,066 INFO [STDOUT] (http-localhost%2F127.0.0.1-8080-11) (null: 2, 265): cvc-elt.1: Cannot find the declaration of element 'bpmn2:definitions'
This is my "definitions" node:
As far as uploading your model to guvnor, you can just place your classes in a jar and upload it to Guvnor New->Model (jar) I believe. Then build your package. The reason your process does not open in Guvnor is most likely something else, the web Designer is not able for some reason to parse your BPMN2. Are you using the jbpm-installer? If so what version? Need to find out the version of the Designer and please paste your process bpmn2 so we can test it as well.
Hope this helps.
Replace your definition tag with this and try again:
<?xml version="1.0" encoding="UTF-8"?>