cPanel has the bad habit of displaying 4 when it should say 2 and 2 - it's 2 mysql, 2 postgresql. That said, I'm not even sure PostreSQL works, but when I inquired to admins about it, it sounded like that part may be out of our control.
You should still be able to use Table Prefixes with most software though, which would allow you to install multiple different scripts into a single database, as long as each script uses a different prefix (such as wp_ for wordpress, phpbb_ for phpbb, etc.)