Here's a great example of orphaned software getting a new lease on life. Ambrosia Software created a great little shoot-em-up, Asteroids clone called Maelstrom. It was a little game for the Mac that I played circa 1993. At the time it was a sight to behold-- beautifully pre-rendered 3D sprites, taking fullscreen advantage of those big, 12-inch color Macintosh screens (gasp!). Well, the company doesn't maintain it any more, but they did the gracious act of GPL'ing the source code. That means that anyone can then take it and do what they'd like with it (as long as released derivatives of it also include the source code).
When Ambrosia stopped working on Maelstrom (which was Feburary 15, 1996 according to the FAQ), it was on version 1.4.3, and it only ran on a Macintosh. Today, (thanks to the efforts of Sam Lantinga and others) you can download Maelstrom 3.0 for MacOS Classic, MacOS X (as a native Carbon app), BeOS, Windows (95 up through XP supported) and Linux no less. Plus there are additional sprite and sound packs available. It even has multiplayer support.
Kudos to Ambrosia Software for loving Maelstrom enough to set it free.