Apple are providing authoring tools for their "iBooks 2" engine and are not out of line expecting a cut of the profits...
I think the ownership is about the output format, not the contents itself, so it could be better compared to InstallShield, for example. It is used to package and easily distribute/install your Windows programs.
If it was free but they'd requested similar conditions to those in the iBooks EULA (that you can only distribute it in their own channels, that they might reject your program if they don't like it, etc.), would you still consider them for distribution?
The author is not saying that apple does not deserve a cut. He is noting that it is questionable whether Apple should be allowed to restrict the distribution channel