Sorry to bump this topic, but I'm not a frequent visitor around here and I thought some issues with this needed to be addressed.
First of all, the Wikipedia definition of Abandonware is somewhat flawed, and that article on the whole is a complete mess.
Secondly, abandonware is not legal. Period. Unless you live in a country that isn't a Berne Convention Signatory it's illegal where you live, too.
Thirdly, oldwarez is easy to distinguish: it's "old" games which are still being sold.
A
FAQ I wrote with a few others some years ago is a good jumping-off point for a document such as this. That FAQ traces it's roots back to the original Abandonware FAQ and is far more authoritative than Wikipedia. I like Abandonia a lot, and I think it's great that it has such a vibrant community, but Abandonware is not a new idea and I've noticed some major confusion about it over here from a few different people recently.