Let's lay things down:
- is where people used to CodeHaus Mojo (those using the plugin but never contributed or even looked at its code) will go looking at to report issues
- has its gh-pages available at www.mojohaus.org/gwt-maven-plugin/
IFF MojoHaus eventually change their redirection rules from mojo.codehaus.org to preserve the requested path, then all the old links would come back to life
People used to CodeHaus mojo will also naturally try to just change mojo.codehaus.org to www.mojohaus.org to try to read the docs (I've actually had an edit in StackOverflow where the editor did just that, without even checking whether the new link actually worked).
Having the website under www.mojohaus.org makes it clean that this is a MojoHaus project. I don't know if it has any weight in the balance, but I thought I'd just throw this here anyway.
- is known to all people having looked at the code and/or contributed patches
- is next to other projects related to it in the gwt-maven-plugin organization (those projects appear long dead though; last update 4 years ago)
- there are really few links to it out there (compared to links to the old JIRA for issues, or the old doc at mojo.codehaus.org)
I think that when you rename/move/transfer-ownership of a project in GitHub, they automatically do a redirect. So it would probably be possible to delete the repo at mojohaus and then transfer the repo from gwt-maven-plugin to mojohaus (maybe first check with GitHub support).
Or the mojohaus repo could be emptied, with just a README linking to the "real" code repo, and with wiki and issues hidden/disabled, and kept only to host the gh-pages so they appear online under www.mojohaus.org
I don't have a strong opinion one way or the other, but I think there are many advantages to having the docs under www.mojohaus.org
(particularly IFF they eventually change the redirection rules from mojo.codehaus.org
to keep the requested path; so maybe check with MojoHaus first about their future intents), and some more to having everything (code and issues) under the mojohaus organization as well.
There are only few drawbacks to killing the gwt-maven-plugin repo (and organization altogether) and moving everything to MojoHaus, maybe the biggest one is managing committers, but I think there's been some changes at GitHub lately such that at least it shouldn't be a showstopper.
It would also be useful to know whether MojoHaus would migrate the old JIRA issues to any repo (provider they're given API access to it), or only to ones that are under the mojohaus organization. That would possibly weigh in the balance.
Oh, and BTW, should that Group be renamed too?