As you may have seen at PASS Summit 2017 or another event, with the announcement of Azure Data Factory v2 (adf), Biml will natively support adf objects.
Please note, that the native support is currently only available in BimlStudio 2018. If you’re using BimlExpress, you can still generate the JSON for your pipelines, datasets etc. using Biml but you cannot use the newly introduced tags.
The really good parts are only available in the paid product; if you do a lot of Azure Data Factory work, that might tip the scales in favor of getting BimlStudio.