@braden Thanks for reply. I posted a more general question about extension options and licensing options having read / searched some more: Feature extension / plugin options and licensing options
I think my take on this is in line with what you say - if you are using via an API then you have a free choice. However like you Iām not, nor ever want to be a lawyer 
If you have any comments on the actual extension options, API docs etc then be happy to get them on that thread.
Thanks again.
Rick