Yep sounds right, get a free technology, make it a proprietary solution, do not give anything back to the community, sounds like Amazon :D
I think nowadays MariaDB can reach Petabytes of data, they have built a new column store engine and they will release a new technology to scale and paralel queryes (Clusterix or something). The costs would probably be a factor smaller than AWS and it's open source. It can read from any ODBC source as well, from multiple parallel sources acting like a live catalog for an warehouse.
Has MariaDB replaced MySQL? Is there a major advantage to using it?
How does it compare to Postgres/PostGIS?
Basically yes. Most MySQL core developers moved to MariaDB, and they added the features that MySQL corporate version has and a lot others on top, for free. They made a foundation and a license that guarantees it will be public all times, so what happened to the product when it was bought by Oracle would not happen to Maria, even if the Foundation is bought.
As for the reasons why you should not use MySQL anymore here are a couple, including that many Linux distros dropped the support for MySQL and moved to Maria.
Postgres has the same downsides and limitations as MySQL and a worse license and dev policy from what I heard (its owned by one company and keep a lot stuff secret and take arbitrary product decisions).
Thank you @bgadrian
for the detailed response and references.
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