Hi Adam,
Thanks for the response.
I think a rate limit on the API for Free licenses would be fair - I'd prefer that to a capability restriction in any case :-).
The script I've been working is an evolution of a very basic one I wrote about 5 years ago that simply deletes the *.nupkg files off the filesystem storage if they're older than a certain date, so the package versions that my new one is deleting via the API are mostly a historic backlog of the version "stub" records - going forward the daily deletions will be a lot fewer so a rate limit wouldn't be an issue.
This is all part of some work we're doing to migrate our Azure VM-based ProGet Free instance to an Azure Kubernetes container instance - we actually got it working pretty quickly and we're happy we can remove another VM from our infrastructure landscape.
It's also going to allow us to reduce our Azure resource costs by quite a bit, so I'm hoping I can make a case to our team lead that we should re-invest that in an annual Basic license to take advantage of some of the additional features - I'm particularly interested in the package scanning and license scanning capabilities so 
.
As an aside, I did find a small snag with the official Inedo ProGet container registry - it was mostly a problem our side but I'll post a separate ticket about it for completeness...
Thanks again.
M