I want to buy the MAC OS X operating system from Amazon and wanted to know if it can be install in VirtualBox with Linux as the host machine?
Lifehacker has an article describing how to install Mac OS X in Virtualbox.
This article over on Lifehacker shows that it can be done with virtualbox on windows. I don't see why virtualbox on Linux should be any different.
You don't need the hacked DVD discussed on lifehacker.
http://www.sysprobs.com/mac-os-guest-virtualbox-326-snow-leopard-1064-windows-7-32-bit is for VirtualBox 3 something, works on VBox 4.x as well. The only thing you'll need to do, is get the boot CD, which is discussed in the article.
When installing, it will not find a disk--use disk utility from the installer to create a partition, then it will see the disk.
As for sound, note that the links provided are for the AC97 driver--VBox's default sound is Intel, so you have the change the default setting.
Also, do note that as mentioned, probably not legal according to the EULA, but most EULAs are of questionable legality if taken to court.
So, you do not need a modified install DVD anymore, but you will have to download the bootloader.