I want to point out (if you're not aware) that pretty much all of the viewers simply pull out the *embedded* jpeg that lives inside the raw file. So, if you really want to see the raw image, you need to go the extra step ala fastrawviewer.
Also note that the licensing is OS independent so 1 $15 purchase covers your Mac and PC.
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The purchased License is OS-independent, and can be used to have FastRawViewer activated on up to two computers simultaneously, as long as each computer is owned by you and you are the only one with access to FastRawViewer
You may transfer the license from one computer to another, provided the terms of ownership are followed, by de-activating FastRawViewer on one of the computers that have it active and activating it on another one.