Every ops group should support 2 db's: a free one and a non-free one. You use the free one where you can, where it makes sense. You use the non-free one everywhere else.

And please do not ask your ops group to support more than 2 db's.

It is strategically imperative to add a free db to the mix if only to give you some leverage over the non-free vendors. Otherwise Oracle will bleed you. So OK they're going to bleed you anyway but maybe not so badly.