If your appli­ca­tion is a native FreeB­SD appli­ca­tion, it can not use the v4l-linuxulator stuff. If your appli­ca­tion is a lin­ux appli­ca­tion, it will use the v4l-linuxulator stuff and can not use the FreeB­SD v4l inter­face direct­ly. All you have to do is to get your appli­ca­tion work­ing, you do not have to care about which v4l inter­face (FreeB­SD or Lin­ux) you are using, this will hap­pen automatically.