I got in a discussion behind the walled garden of Facebook about hymns, copyright and what we (as ministers and content providers) and I've brought some of my comments here. In particular, what do we do with hymn texts we think are in the public domain, and thus subject to republication, reuse or adaptation. But the text may seem a little one-sided…
It's easier to show something is in copyright, than prove that it's not. The before-1923 date is true, but there are works up to 1977 (when the law changed) that may be in the public domain. And that doesn't got into the issue of licenture, including permissive licenses; see Creative Commons. It's a tricky business. A fun place to start: http://librarycopyright.net/resources/digitalslider/
Another thing to keep in mind: liturgical elements that ministers write. Each of us have created copyrighted content. You don't need to register an item to have copyright anymore. We can give permission each time (a pain), watch our works get cribbed without permission (annoying) or have it left untouched by the skiddish (a waste).
We can be good model of stewardship by providing our own "some rights reserved" licensing, using a Creative Commons model license. I've written about it, and license some works, but the Open Siddur people make a strong, maximalist case for licensing creative works, so they get the link. http://opensiddur.org/decision-tree/