I don't think they would give you the source to the OMS, but they have a little bit of documentation on modules if you ask. Their sample projects are written in C++ with visual studio.
https://www.getafreelancer.com/projects/Trading-Platform-Alteration-GNDT-com.html I'm on the look out for a programmer
Without the source code, you must re-create OMS from scratch using the API and then add a lot of GUI and persistence features to make it faster to enter stop orders. If it were simple, Genesis would have done it by now. Another thing to consider: if you spend money on this effort, there's nothing to stop Genesis from cloning it once you've got it up and running. The hard part is designing the GUI and data entry methodology....and they've been very weak in that area.