OEM= Original Equipment Merchandise. It can not be sold separate of the machine that it comes bundled with. I know on Ebay sellers "get away" with selling a hard drive or video card, and throwing in the software. Actually they sell you the software and throw in a broken piece of hardware.
BOX= just like it says, they send you the program CD/DVD, and maybe a manual (booklet) in a BIG box. It can be an upgrade or full version.
UPGRADE= Full version, except it will require either having a previous qualifying version installed, or at least the serial number, to install and use it. The price is discounted.
FULL = The whole thing. You would need to purchase a full version if you do not have a previous version, or you just don't want to keep the previous version installed, or you lost and can not retrieve the serial number, proof of purchase for the previous version. It costs more then the upgrade.
RETAIL = Generally means that it is sold by "real" stores, like a computer shop.
Yep, currently I have, VS 10+, VS11+, DVDMF6+ and MSP8 all installed. They are free standing, and co-habit well. There are some issues with VS11+ and DVDMF6+, but I think that is mainly geared toward the High-Def video.