Answer: 

First, know that OPIM is a separate application from AutoPIPE. Thus OPIM software must be downloaded and installed separately. 

To answer the question, Can a Stress Isometric be created without an additional OPIM license?

Yes,  an OPIM license is not required, nor will you be charged for its use when using AutoPIPE Advance, AutoPIPE Nuclear, or Virtuosity AutoPIPE Advance. If user only owns AutoPIPE Standard or Virtuosity AutoPIPE licenses, regardless of OPIM installation and license, then they would be blocked from generating a Stress isometric. The ability to generate a Stress isometric is hard coded to having an Advanced or Nuclear license. 

Note, if OPIM software was accessed directly without using AutoPIPE, then YES the user will need a OPIM license and usage charges will be incurred.

Again, use AutoPIPE commands:

a. Save Stress Isometric (File > Isometric > Save Stress Isometric)

b. OpenPlant Isometrics Manager (File > Isometric > OpenPlant Isometrics Manager)

Note: an AutoPIPE Stress Isometric drawing can be viewed with Bentley View without any usage charge against OPIM Licensing.