No, they are most definitely not the same company - and there is a big difference in the two products.
Tim DeBenedictus and his team used to work for CarinaSoft developing "Voyager" for Mac and Windows. They started developing "Sky Voyager" for iDevices a couple of years ago for that same company. After some managerial issues within CarinaSoft, Tim et al left and formed their own company - Southern Stars. Here they developed Sky Voyager for iDevice which was renamed SkySafari some time later.
See the story from the man himself here:
http://www.cloudynights.com/ubbthrea...8/Main/4312056
Seems silly, but I gather that Southern Stars has allowed Carina to sell the defunct SkySafari v2 under its own name. If you look at the copyright info on iTunes, it states "Seller: Carina Software, ©Southern Stars." Consequently, SkySafari 3 states "Seller: Southern Stars, ©Southern Stars."
So, what Southern Stars sells is v3. At the end of the day, go for the Southern Stars offering, not Carina.