A participant can join a second and subsequent projects as follows.
If a participant joins multiple project, his/her preferences will be propagated to all the projects, and can be edited on the web sites of any project. Propagation may take several hours or days. If preferences are edited at one project, then edited soon thereafter at another project, the first edits may be overwritten and lost. This can be avoided by only editing preferences at one project.
Some projects may provide a web interface for editing their project-specific preferences. In this case it may be necessary to edit preferences at different sites. To avoid overwriting edits, wait until previous edits have propagated to a site before editing preferences there.