I really like Robin Harris' Storage Mojo blog, but in this case, but i'm thinking in his article Why did Apple drop ZFS he is wrong, when he thinks that the CDDL may posed a problem: Mac OS X uses Dtrace for a while now and it's licensed under the CDDL as well. So this can't be the reason. I assume some technical problems, but at Apple this includes "Steven didn't like the graphical user interface". Considering that this was a release concentrated at the inner workings of MacOS X, they didn't wanted to introduce a completely new feature to reduce potential instabilities because of newly introduced code. I don't even think a GPLed ZFS would help, given that a GPLed ZFS would introduce the same kind of problems for MacOS X than a GPLed Linux has with the CDDLed ZFS.

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