This looks like the free/open-source version to Sendy based on more modern tech like Golang/Docker/etc I've been hoping for, congrats on your alpha release!
Thank you. It was a bit of a surprise to me that Sendy had no viable open source alternatives. phpList is okay, but is quite dated and has a number performance issues.
I've also been a Sendy user for a long time for non-critical applications, and I don't like the fact they hide their code so a tool like this is long overdue and much needed.