People outside of IT seldom think of Oracle as a Linux company, probably because it isn't. Oracle has always been considered a database and application company. Their main bread and butter is the Oracle database (currently at version 11g), and the application products they have acquired through PeopleSoft, BEA Systems, and other companies. They also offer a product called Oracle Unbreakable Linux (a clone of Red Hat Enterprise Linux), but it has never achieved the wide market share that Red Hat currently enjoys. So now that Oracle owns their own operating system in the free and clear, what benefits do they gain from maintaining Unbreakable Linux? The answer is probably: "Not much".
Oracle Unbreakable Linux was originally designed to be a Linux distribution backed by Oracle's support group, which is considered superior to the support offered by Red Hat. It gives their enterprise customers a better sense of security knowing that they can get operating system and database support from a single vendor. It also provides a platform for Oracle contributions to Linux. Oracle has contributed improvements to libstdc++, NFS, ext3, and they are the original creators of the Btrfs filesystem. Those contributions are being made to ensure that Oracle runs great on Linux. But while they contribute a lot of code, they don't actually own the Linux kernel. Every Linux distributor can use Oracle's contributions, and the only true benefit Unbreakable Linux offers is their support package.
But now that Oracle has acquired Sun, the landscape has changed. Oracle can still continue to support Linux, but nobody is ignoring the fact that they now own the copyright to their own operating system. Linux vendors like Red Hat cannot benefit from improvements made to the Solaris kernel, in contrast to the contributions Oracle made to Linux.
It would also be negligent to ignore the fact that Oracle and Sun have maintained a strong relationship for over 20 years. In 2005, Oracle named Solaris 10 as the preferred development platform for all 64 bit hardware (that's UltraSparc, AMD, and Intel). Oracle on Solaris has a stronger market share in contrast to Oracle on Linux, so it makes sense for Oracle to continue backing the platform that is trusted by more customers.
As far as features go, OpenSolaris has ZFS, container virtualization, role based security, network virtualization, and dtrace. Linux has spent the last six years playing catch up with a lot of these features, and they're still not 100% there yet. By the first quarter of 2010, OpenSolaris users will have a default filesystem that supports encryption and de-duplication. In contrast, Red Hat Enterprise Linux users are just starting to get their feet wet with ext4, a filesystem that has no real notable features whatsoever.
If Oracle had to take a serious look at these the feature sets between Linux and OpenSolaris, which one are they most likely to put their money on?
Oracle could still make contributions to Linux, but sooner or later the shareholders are going to ask why Oracle is using time and money to write code that inevitably helps Red Hat and Novel build a better product. Efforts at contributing to Unbreakable Linux will probably be better redirected in convincing customers to migrate to a more stable enterprise level operating system.
I hope that isn't the case, because Linux has benefited from the contributions made from Oracle. Without those contributions, it's unlikely that anyone would have deployed Oracle on Linux at all. And now that Oracle and Solaris are under the same umbrella, what reason do they have to stay with Linux?