There is an online dataset that is freely available (though the licence and copyright situation is unclear). Users are actively (and voluntarily) contributing minor corrections and additions via forum posts. These users are not explicitly claiming any copyright, but nor are they explicitly dedicating their contributions into the 'public domain' or similar. The posts are collaborative in nature - users are deliberately contributing corrections with the hope that they make their way in to the master dataset for the benefit of others (similar in spirit to how people make contributions to open source software).
It's clear that these contributions are being 'given' to the public domain (in the general sense), but does that mean that they are in the public domain (in the legal sense)? Are these corrections/additions convered by any copyright?
(if relevant I think the appropriate law in this case would be UK law, as the users and website are all UK-based)