OpenFlows product license usage will start when the .DGNLIB file for the OpenFlows product is opened.
This occurs when clicking "Open" in MicroStation's File Open dialog while a user and/or project is set to the OpenFlows product ("WaterGEMS" in the example below). The OpenFlows product is selected as the user/project when you launch the shortcut "<OpenFlows product name> for MicroStation"
Note that when working in the "...for MicroStation" platform, license usage of both the OpenFlows product and MicroStation itself will be recorded.
Hydraulics and Hydrology Product Licensing (Activation) FAQs and Troubleshooting [TN]
Troubleshooting MicroStation Integration
Loading Hydraulics and Hydrology products into a custom MicroStation workspace