I used to have my process deployed with async="false" nodes. Limiting the number of concurrent processes was as easy as limiting the CommandListenerBean MDB pool size.
Because of very long transactions the synchronous execution required, I had to make some of the action nodes asynchronous. I wonder if anybody has some advice concerning the limitation of the concurrent number of async="true" processes.
My novice understanding of jBPM says that the number is only limited by how many messages your queuing system can store. No inherent limit in jBPM exists.
Hopefully a more knowledgeable expert can confirm my understanding.