Digital media presents an interesting new twist as you may provide the RightToInclude without the RightToDistribute?. Consider TransClusion. Under existing copyright law, most believe or at least fear that TransClusion is not permitted by the default copyright law (e.g. the BerneConvention). After all, the process the medium uses to compose the content presented is irrelevant from the reader's perspective as she will only see one unified work. That means the reader will interpret the two digital sources as one work, even if clearly marked as separate. From the perspective of literary theory, that is also the case, as composed together the multiple sources form a new original text. That suggests very strongly that transcluding material directly into a text creates a derivitive work. Even if legal cases about this are vague and unsettled, presume this is the case.
To solve this problem TedNelson created the concept of TransCopyright, a very complex digital method of controlling the use of works on per user basis. While not necessarily irrelevant, it has bad FeatureKarma. Instead it is simpler just to provide the RightToInclude your text, or parts thereof. Even if you do not permit redistribution, other parties online can simply transclude your text directly into theirs. Thus, you can control access to the text and guarantee that all derivatives are up to date.
Another way to fight ContextSwizzling and the next best thing to keeping derivatives up to date is the "RightToInclude with citation". That is, anyone may include the text, but they must cite the work that it came from. CreativeCommons may eventually provide a [license option similar to this].
A document that includes another document via the RightToInclude may be licensed under the FreeDocumentationLicense, but only where the included text is OffTopic, so it may be regarded as a secondary section.
It is needless to comment on the hugeness of the CopyLeft movement on the Internet. The reasons to grant the RightToFork are well-known and explained elsewhere. However, commonly the presumption with the RightToFork is that the work under license is an objective, formal artifact. When considering ForkingOfOnlineCommunities, things get murkier. While common objections to forking online communities are social costs of splitting the community, another serious problem is giving away control of communal discussion. When you consider that OnlineCommunities are LifeInText, the potential pitfalls of allowing unknown and probably hostile third parties to ContextSwizzle? and ContentSwizzle? your ThreadMode are immense. When we are just dicussing ideas informally, it makes little sense to allow others to fork these ideas. Things get worse if your corpus includes a DiaryCollective? as a subset, let alone FrontLawns and MessageBoxes.
Yet sometimes you want other people to be able to reuse your material, say if you feel that it is a waste of your time to contribute to a CopyrightTrap. You can limit how people (at least legally) use your work by only granting the RightToInclude. They cannot edit your unpolished text. If you demand accreditation, they cannot quote your words out of context as you can always force them to display a hyperlink to the original source. If you only permit TransClusion, you have even more control. Furthermore, inclusion is a strong advertisement for your community. If someone else felt strongly enough to include text from your community, clearly your community is better than theirs for at least that discussion. A full citation will pull people towards your community rather than encourage others to stay elsewhere, akin to the Wiki:WikiGravitationalEffect. Thus the dangers of ForkingOfOnlineCommunities are somewhat (greatly) relieved.
Meanwhile, others benefit by being able to create derivative works from your own. At the very least they may make a compilation, but they may also annotate your work if they wish to derive more richly from it. Although they may not modify your work directly, if your source community was a wiki, they could always just edit the document on the source wiki. They may prefer editing the document in its home context, as clearly the experts on the field are the ones who wrote that document. The benefit of providing hyperlinks directly to the source are apparent here. They may also mirror your work at will, thus providing a potential afterlife to the text after your community's death if that is important to some.
However, if your community does die no one could resurrect it. You may put a provision to allow others to resurrect it after a sufficent time period had past after death, possibly being 0 seconds, although copyright normally expires 70 years after the last author's death. 70 years after the community's death may also be appropriate.
Note that your content is not dead during this period. They may still mirror it, annotate it, and of course criticize it through FairUse.