InfraRecorder is another free, open source burn application that is simple, powerful, and burns both CDs and DVDs. It uses source code from cdburnerxp, and can be portable using InfraRecorder Portable.
To burn the ISO, open InfraRecorder and click on "Write Image". Search for the location of the PC-BSD image with the extension .iso at the end, and double click it. Lastly, click "OK", and watch it burn.
When it is finished, the tray with the DVD will open and a dialog box will appear indicating that the burn is finished.