I am neither for nor against the Oracle-Sun merger. I am against the damage done by extending the uncertainty on the outcome of the deal. MySQL as an organization is in great shape. The 5.1 release turned out better than some expected. The InnoDB plugin is excellent. What is the roadmap? MySQL is limited in what they can say about their future. That hurts all users and customers.
A lot of nonsense has been written about this. As MySQL employees cannot write about it, the discussion has been one sided, full of speculation and justified by quotes from random people. I almost provided a few quotes myself when contacted by someone I thought was a potential MySQL customer.
I am neither a lawyer nor an economist, so I don't understand their notion of competition as applied to this issue. I wish that were clear. I don't think that the 8-year old E-Week benchmark implies anything about whether MySQL and Oracle compete. Nor do I think that a few slides from a project at Sun that failed to migrate Oracle customers to MySQL is evidence of that. Marten's letter set a high standard for the discussion. I hope others follow it.
Clearly competition isn't defined by revenue as that is something between $100M and $300M per year. The database market is much larger than that. For better or worse, MySQL has not done a good job of monetizing their users. Maybe they have not tried to do that as their value seems to be independent of their revenue. But someone has to fund the development of MySQL.
I have worked on source code for the Oracle and MySQL database servers. I have used MySQL in production. Some parts of MySQL are amazing (InnoDB, JDBC, support, docs, bug database, server uptime, ease of use, NDB) but in no way do they compete on a feature basis. I hope that never changes as MySQL would be ruined were it to become as complex as Oracle. I am sure they compete for some customers who don't need all of the features provided by Oracle. But that competition includes Sybase, Microsoft and IBM.