Not a full replacement but there is Garage, which was quite well received in other HN threads.
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They are also a comparatively young project and while fully OSS do not, afaik, appear to have a solid long term funding source yet. Though that might be an opportunity to support them, if your company is interested in picking them.
[0]: https://garagehq.deuxfleurs.fr/documentation/reference-manua...
This is a set of unofficial Amazon AWS S3 compatibility tests, that can be useful to people implementing software that exposes an S3-like API. The tests use the Boto2 and Boto3 libraries.
https://github.com/ceph/s3-tests