Most are free-to-use (ie public domain or copyright-free), so words can be copied and sung to at least one tune with no concerns about copyright or performance licensing. Many such hymns are old/traditional - but where possible a variety of styles / genres are included. A few hymns which may still be copyright may also be included, if they are particularly appropriate.
Suggestions about hymns that could be included are welcome: leave a messages in the Comments box near the bottom of the page.