You can check your panel for PHP. Go to https://panel.dreamhost.com/index.cgi?tree=domain.manage& and click on ‘edit’ (I see you’re on 5.3). The lowest we offer is 5.2 though, so you should be okay anyway!
MySQL is on at least 5.0, the exact version varies, but it should be compatible with just about anything.
Mod_rewrite is always on, safe mode is off.