The Mac OS comes free with a Mac. New versions have a small charge.
There is currently no version of Pivot for Mac OS X, free or otherwise. An alternative would be Stykz which is available for Mac OS X and is free. (See links below)
nowhere, just use crossover on mac OS x.
Mac OS X - no doubt about it.
A legitimate copy of Mac OS X 10.4 will only be available to buy.
GIMP for Mac OS X can be downloaded from the GIMP on OS X web site. (See links below)
it is illegal to do this
Ask for it for your birthday or Christmas.
Yes, there is Pencil, and it's free. There are many versions for it like Mac OS or Mac OS X. Personally, I just got it and it sucks.
Skype for Mac OS X can be downloaded from the Skype site. (See links below)
It will depend what you are trying to achieve and how you define better. If software is written to use Microsoft's Windows system and is not available for Apple's Mac OS then Windows would be better. If you are using a Mac made by Apple then the Mac OS would probably be more suitable but you can always switch to Windows on a Mac if needed. If you are looking for a cheaper, virus free, trouble free computing experience then Mac OS would be your choice.
Yes. It's available for Windows and Mac OS.