Online services are one of the easier licensing models from Microsoft. Yet, even simpler are developer tools – one license is required for each user that accesses the software. Regardless of how many copies are installed on however many of devices, each user must be licensed individually and the software must be used only to “design, develop, test or demonstrate” programs.
In order to remain in compliance, be absolutely sure each user is licensed properly and you use the software as intended for development and development only!