That's a a really interesting development. Mårten Mickos, the former CEO of Mysql AB, wrote a letter to Mrs. Kroes, the EU Commissioner for competition. It's an really interesting read. The document was published in the article "Mickos letter to EU: Approve Oracle-Sun deal" in Matt Asays blog at CNet. I will just cite the closing words here:
In closing, I would ask that you, Commissioner Kroes, consider the market dynamics and the facts. Every new day of uncertainty is potentially very harmful to the various businesses of Sun, reducing competition in the market. A delay in the closing of this transaction is therefore only going to work against the respectable goal that you set out to achieve when launching the probe into this acquisition.

I believe that Oracle's acquisition of Sun (and MySQL) will increase competition in the database market. And I also believe that if, on the other hand, it becomes difficult or impossible for large companies to acquire open-source assets, then venture investments in open-source companies will slow down, harming the evolution of and innovation in open source, which would result in decreased competition.
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