Perhaps you should also take a clue and read the category titles.
Nowhere does it say "Best Client OS" It says "Best Client" which in reality, since this is a Product survey means "Best Client Product". A best client product can be an OS, or a removeable media device, or a keyboard, or monitor.
The same applies to the "Best Server" category, in which a backup product, network card, and network printer are all server related products.
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