The free software world, as in any other field of human endeavour, has people and their interests come and go over time. This can leave projects unmaintained, but it is not necessarily the end of the world. Because of the licenses that are used others are quite free to take up the reins and resurrect a project (as myself and Brian have done with the Vacation program).
The real issue is people knowing about the projects in the first place, and so the Unmaintained Free Software Wiki was born.
Few people seem to know about the site though; Jon Corbett at LWN puts it like this:
Unfortunately, this project itself looks like it could benefit from a bit of maintenance. Only seven projects have been added since the beginning of the year, and only two (Gnome Commander and khtml2png) are listed as having been adopted. Perhaps the problem is simply one of awareness; If relatively few people even know that this site exists, few are unlikely to make use of it. If that is the case, then, hopefully, this article will help a bit.
So I’m hoping that this will help spread the word as well. If you like the idea of this then I encourage you to blog about it too and, if you have the skills, enthusiasm and Copious Free Time, take on a project yourself!