Once again I was asked if the GPL of Imixs-Workflow does affect the development of a proprietary application which is distributed under a non-gpl licence? The answer splits into two different aspects:
Running a Separate Process
Since the Imixs-Workflow engine runs as a separate process which is called from a closed-source program, the FSF presents the legal opinion that the proprietary application would probably be a separate work. And this is the typical usage of the Imixs-Workflow engine. This is also valid if you develop a library or a plugin linking to the Imixs-Workflow engine used from a non-free program. The copyleft of the GPL library causes your plugin or library to be covered by the GPL, but not the main application, which is probably a separate work. As long as the workflow engine runs as a separate process there is no violation of the GPL in your main application.
Distributing Software
The second part of the answer is about the question of distributing software. In these days we all mostly develop software running on servers in the internet or the ‘cloud’. In this case it does not matter if your server uses a GPL library or software like MySQL or Imixs-Workflow. As long as you did not distribute the source code of your software you are not affected by the GPL or violating it. You are totally free to use GPL software.
Conclusion
Does the GPL of Imixs-Workflow affect your application development? The answer is “no” for the cases discussed above. Feel free to use free software, but avoid to prevent others from using free software.