On FMS 13 there is a new licensing..
This special, test-only version includes all the features and functionality of FileMaker Server 13. Please note that the Development License only allows up to three simultaneous FileMaker Pro 13 and three simultaneous web-based clients for Custom Web Publishing, and one FileMaker WebDirect connection to access hosted FileMaker solutions. For FileMaker Server 13 Development License system requirements, see FileMaker Server 13 requirements.
You only get 1 web direct license / Go License. We really need at least 5 to test with!!! Come on FileMaker... Help us out here!!! And to top it off you can't even add licenses to the Development server.. URRR... Don't get me started on this one...