I have no idea, experience or opinion about Oracle. But if you just want to use SQL on Linux, there are lots and lots of choices.
MySQL and PostgreSQL are both very available and very popular.
My Mandriva machine is off at the moment, but on Fedora, this command reported
528 lines. Many of them are development libraries or plugins or double-line entries, but it still indicates there's lots of software available for free.
Code:
yum search sql | wc -l