I think this page describes abandonware pretty good:
http://en.wikipedia.org/wiki/Abandonware
"Definitions of "abandoned" vary; generally it refers to a product that is no longer available for legal purchase, over the age where the product creator feels an obligation to continue to support it, or where operating systems or hardware platforms have evolved to such a degree that the creator feels continued support cannot be financially justified. Software companies and manufacturers may change their names, go bankrupt, enter into mergers, or cease to exist for a variety of reasons. When this happens, product rights are usually transferred to another company that may elect not to sell or support products acquired.
"Abandonware" is a term created with no legal basis so it's not recognized by the courts. It's illegal to trade in it, it's a question if you will get caught and if there will be anyone that will seek a penalty.
