Elizabeth
I'm not sure the society has claimed copyright - if it had (which as I commented is the position re academic journals and which, in my then ignorance, I thought was the case) then life is much easier - the Author can re-use the material, the society can arrange publication channels - copyright is a minefield and to be honest I only began to realise some of the problems after I started. During the brief period I was editor I added a clause to the front page of the journal stating what I then understood was the situation re copyright (I think in a subsequent edition the new editor misquoted it effectively inverting the situation !).
In practice, I believe, infingement of copyright, except for purposes of gain, is a civil offence and as penalties are usually related to the benefit derived (in my case nil) or revenue lost by the holder (again presumeably nil) , then the usual penalty is a notice to remove the material (American law is now different but most of the RIAA cases against file swapping that made the headlines re sueing of 14 year olds etc have actually never come to court but rely on the exceedingly high cost to the individual of fighting a legal case in that bastion of capitalism which as the saying goes 'has the best law money can buy' thus forcing the private individual to settle out of court.
However I should add I am not a lawyer.