Unless something has changed since last year, it is not truly "open source" if you're going by the Open Source Initiative's definition of "open source".
Evidently there are a number of restrictions placed on the source code that prevent this from being the case. There was a Reddit discussion about it at the time:
In my university we have been using remote VMs with a GUI (e.g. Windows) for more than 10 years. We need to this with several softwares due to license restrictions.