O365 licensing datasource?

PWheeler You can do it by accessing MS Graph:
https://graph.microsoft.com/v1.0/subscribedSkus

You need to give your account permissions listed https://docs.microsoft.com/en-us/graph/api/subscribedsku-list?view=graph-rest-1.0&tabs=http 

{
    "@odata.context": "https://graph.microsoft.com/v1.0/$metadata#subscribedSkus",
    "value": [
        {
            "capabilityStatus": "Enabled",
            "consumedUnits": 1,
            "id": "xxxxx-xxx-xx-xxxxx-xxxxxxxxx-xxx-xxxx-xxx-xxxxxx",
            "skuId": "xxxxxx-xxxxx-xxx-xxxxx-xxxxx",
            "skuPartNumber": "O365_BUSINESS_ESSENTIALS",
            "appliesTo": "User",
            "prepaidUnits": {
                "enabled": 1,
                "suspended": 0,
                "warning": 0
            },
            "servicePlans": [
                {
                    "servicePlanId": "xxxxxx-xxxx-xxxxxx-xxxx-xxxxxxx",
                    "servicePlanName": "MICROSOFT_SEARCH",
                    "provisioningStatus": "Success",
                    "appliesTo": "Company"
                },
                {
                    "servicePlanId": "xxxxxxxx-xxxx-xxxxx-xxx-xxxxxxx",
                    "servicePlanName": "WHITEBOARD_PLAN1",
                    "provisioningStatus": "Success",
                    "appliesTo": "User"
                }
            ]
        }
    ]
}