DOAP stands for "Description of a Project" and you can find out everything there is to know about DOAP here.

That's a very good question! The answer is that generating a DOAP file should take no effort if you are using Maven DOAP Plugin and it helps disseminate project information which can only be a good thing. Cataloging tools like CodeZoo and SWiK can benefit from you generating DOAP files and that can also only be a good thing. Ultimately the Maven team plans to provide an index of all POMs that have been submitted to the central repository so we are most likely going to have the most up-to-date information about projects. Even so, it is still important to spread as much information about projects around as possible so there is no downside to creating DOAP files.