I also think there are established communities (and codebases) that have existed for decades built around some of these products (like Oracle or DB2 on the mainframe). This is also a consideration for many organizations large and small.
I'm not saying that the open source solutions can't be competitive from a technological standpoint, simply that they have to win on cost, availability of experienced people for dev and admin, and overcome what amounts to a late start in the market.
Plus, on the low end of the market, aren't there express editions of SQL Server and Oracle available for free? For lightweight use these would seem to be reasonable competitors to open source.
I'm not saying that the open source solutions can't be competitive from a technological standpoint, simply that they have to win on cost, availability of experienced people for dev and admin, and overcome what amounts to a late start in the market.
Plus, on the low end of the market, aren't there express editions of SQL Server and Oracle available for free? For lightweight use these would seem to be reasonable competitors to open source.