MariaDB - https://mariadb.org/about/
Amazon have been using MySQL even before all these forks happened. And not only that, if Oracle decided to pursue a lawsuit, or if MariaDB, Percona, Elasticsearch or EnterpriseDB did, Amazon will have to cough up.
This is not really a thing that Amazon should be bragging about, because it makes no real sense! They still run a lot of software they did not write.
Amazon did not replace Oracle with MySQL. You seems to talk a lot given your knowledge of how Amazon operates internally and how licensing works is... blatantly false.
All of those DB's that could "pursue" a lawsuit are built on open source licenses which Amazon is not violating.
But the most important point here: The idea that you have to write a database to be happy to be off Oracle is insane. Amazon moved to an alternative that doesn't have a deep license designed to financially screw their clients as much as possible. That's a win.
2. Open Source licenses that Amazon is not violating - a 3rdparty lawyer would be able to ascertain better about the extent of legality on Amazon's changes and its contribution back to open source software than you and I do.
3. Ex-Amazon employee here. My comments are purely based on my observation - and purely my opinions. Why can't I talk a lot?
2. If there was a means to sue Amazon for hosting databases, Oracle would have already done it a LONG time ago with MySQL. The burden is on you to prove your claim.
3. You are free to talk as much as you want, just expect push back when you aren't right, a lot. ;)
3. Except when the other person isn't. You just lost me on the last comment.
Pursue a lawsuit over... what, exactly?