In recent years, a new category of illegal software has arisen: abandonware. As games age, software companies don't want to provide support for them. Eventually the games become out of print. Fans are interested in playing these games, but cannot find them. Abandonware fills this gap.
Computer games are a relatively new art form, and an ephemeral one at that. Companies crank out games at an ever-increasing rate. In the meantime, given the volatility of the gaming industry, companies are bought, broken into pieces, auctioned off, and merged with other companies. Oftentimes game companies don't know what old titles they own the copyright to. The information is buried in old archives, and may never see the light of day. Meanwhile, warez sites house only the most recent of games, and have no archives of older games.
Enter abandonware. Abandonware refers to games which are effectively out-of-print and unavailable, games which companies have "abandoned". By making these games available, abandonware sites allow new gamers to discover older games such as M.U.L.E. and Star Control 2, or for owners of older games to replace disks gone bad when a company will not or cannot.
Abandonware is a new concept, having gained currency in 1997. In late 1997 the Interactive Digital Software Association (IDSA) and the Software Publishers Association (which merged with the Information Indisutry Association in 1999 to form the SIIA) sent cease-and-desist letters to a number of the nascent abandonware sites, which promptly shut down. However, in 1998 a number of notable sites such as Home of the Underdogs, The Ring of Ages (now defunct), and TUOL were established; since then, abandonware sites have spread like wildfire.
Despite the newness of the concept, abandonware is as illegal as warez. Copyright lasts for 75 years if not renewed; no computer game has yet reached that magic age. As Peter Beruk pointed out, "If an organization goes out of business, and it was in the business of developing commercially-available software, even though that organization may not be in formal existence, that copyright may have been transferred to a third party. If that third party wanted to bring infringement action against an individual, an organizaion, or anything in between, for infringing the rights of the copyright owner, they'd be able to do so."
Despite this, advocates of abandonware strive to adhere to a certain code of conduct. They distance themselves from the concept of warez, avoiding terms such as "abandonwarez" and restricting themselves to games which are at least five years old and are not currently being sold by a company.
A good example of such a site is the aforementioned Home of the Underdogs. Underdogs, the Hong-Kong-based webmaster of the site, created the site in part to spotlight old games which were overlooked by many gamers. The abandonware aspect came second: "My intention from the start was to make a site devoted to underdogs of all ages, abandoned and not; but then, most underdogs tend to be abandoned almost by definition -- poor sales, poor marketing etc. And I thought, well, what's the use of building a site like this if nobody can experience that these games are good? I knew it was illegal, but I always thought of this whole thing on a 'goodwill' basis: abandonware sites are in a sense performing a service to the gaming community, so that (I thought) they would be permitted (indirectly) by game companies to stay alive."