Why openjdk when sun java is open source

I love opensuse, but why is openjdk/icedtea still being installed as the java default when the mainstream version of java (from sun) is open source.
Sorry, but openjdk/icedtea seems to be always several versions behind sun and several thing do not work (ie., WebStart on 64bit computers does not work)

Huh? My understanding is that openjdk IS the open source Java version from Sun.

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