One will wish to be cautious, as they recently changed their license to AGPL-3.0: https://github.com/minio/minio/blob/master/LICENSE because they're afraid of AWS offering Minio as a hosted service, I guess
That seems okay, since you can use any S3 client library. So, good advice, but probably very few folks would have a need to touch the server side source.
Amazon wouldn't, but another cloud service might decide to run this rather than implementing their own S3-compatible object storage from scratch. Or they might use part of Minio's code to make their existing object storage solution compatible with S3.
So that AWS can still get people to pay subscription fees to them, instead of using their own hardware with a FOSS solution, if MinIO becomes too popular.
I understood it as a joke referencing Aamazon's tendency to take just any open source product that happens to gain enough popularity, rename it and offer it as a shiny new feature of AWS.
By "self-hosted" you still mean still running on AWS hardware? I don't understand. Why would anybody pay EBS rates instead of S3 rates, to get data stored in the same place by the same people?
While this is true a word of warning: if you ever end up in a due diligence situation or a source code audit AGPL can really freak people out and hang up/derail the process until you get them to understand this point. If you can at all.
Pretty sure AWS would like to have something that at least looks and feels sorta like S3.
And, being S3-compatible at an API level would be a big bonus for a company the size of AWS, especially if it had nearly native compatibility with the aws-cli tool.