Yes Oracle 11g XE is free although you are stuck a version behind the latest 12c release. You get a lot of stuff in there although you are limited on db size as well. You do get apex which you can use to build web apps easily and all your pl/sql will work but there are some limitations around Java in the database and anything that relies on that. It's definitely worth a go, but if you are starting from scratch Postgres is probably more appealing now.
