Download icloud photo library without paying?
Go to www.icloud.com, select the iPhoto library, and on the top right corner there is an option to mark photos you want to download and download them through the browser. Then you can read them to your photo library on your mac. 

I could not find an option to download all the photos as a "Photos library file" so that one can switch the Photos library directly to it on the mac. But it's at least something.