The other thing to consider is that for me to think that forking makes the future of the project questionable, you'd have to show that it's likely that usage(original project) < usage(upstream) + usage(fork). In other words, I'd be interested to know the combined usage of MariaDB and MySQL and see if you could actually predict with confidence that it would significantly lower than original MySQL usage. Not just that one of the forks didn't have as many people.

Yes, but Postgres had lots of technical advantages of MySQL for years, and still was less popular. For most uses people would decide "MySQL is good enough feature-wise for me. It's so popular it's probably safest ecosystem-wise"

It was the MariaDB fork that shook people up. Now suddenly the decision became "should I bet on one of these forks, or should I skip that drama and use Postgres which seems like a nice stable project" The fork is really what changed the game.

I think most of that was because of Oracle buying Sun. The MariaDB for and Postgres's rising popularity are the outcomes of that.

Original creators left and created MariaDB. MariaDB is now used in place of MySQL in most Linux distros by default. They left after Oracle got control over it by buying Sun (who had previously bought MySQL.)

The short version is that MySQL was acquired by Oracle (when Oracle purchased Sun Microsystems). Following concerns about it remaining open source, MySQL was forked by it original creator, and is developed as MariaDB[0].

[0] https://en.wikipedia.org/wiki/MariaDB

Personally, I always though that the community over-reacted big time. After all, the core DB engine most people were using for MySQL for years (InnoDB) had been owned by Oracle for years before that.

MariaDB has done some decent stuff, tho.