Of course, you’re free to integrate your PMU simulator with MySQL however you like. Here are some potentially useful documents. Keep in mind, they may also be out of date so some of the details may be inaccurate.
Device to Data in 5 Easy Steps describes how to receive PMU data directly into your own custom application, written from scratch using GSF libraries.
https://github.com/GridProtectionAlliance/openPDC/blob/master/Source/Documentation/wiki/Developers_Device_to_Data_in_5_Easy_Steps.md
How to Create a Custom Adapter explains the basics for creating your own adapters that can be used to integrate openPDC with other systems like MySQL.
https://github.com/GridProtectionAlliance/openPDC/blob/master/Source/Documentation/wiki/Developers_Custom_Adapters.md
Two Custom Adapter Examples provides a couple example projects to help guide you to a point where you have a working adapter that can be integrated into openPDC.
https://github.com/GridProtectionAlliance/openPDC/blob/master/Source/Documentation/wiki/Developers_Two_Custom_Adapter_Examples.md