An interesting reason I became intrigued with Postgres in the early 2000s was the license it was/is distributed under. The situation involved some work for a customer that needed to distribute an RDBMS along with their software. The customer had more apprehension around the GPLv2-licensed MySQL than the BSD-esque PostgreSQL License [0], so we went with Postgres.

I later continued using Postgres in my career after having done quite a variety of benchmarks and came to the conclusion that it, in general, scaled more linearly across additional CPUs than MySQL's InnoDB engine did at the time.

[0] PostgreSQL License: https://www.postgresql.org/about/licence/