No derivatives clause
Such licenses aim to protect the work, but from what?
- being altered in ways that might lead to harm being done
- misunderstandings, people thinking that the altered work is actually the work of the original author.
However this clause also greatly restricts the usefulness of the work. Wikipedia, Appropedia and other successful wiki projects have shown the value of a community of editors, or of a single enthusiastic editor being able to modify an article, and add their own particular knowledge.
Note that work under a no derivatives license cannot be used on Appropedia (other than in exceptional and temporary cases as part of the Open access pages policy, intended to serve a need until actual open content is made available).