TonyQ I suspect you can't do what you're asking. The usual reason given is that OpenLP does not know which slides you're actually going to display. For example, you could start a song at verse 2 ...
The "solution" that we found to this was to modify the theme so that the copyright information is displayed very small at the bottom of the screen, and in a neutral colour. That way, the congregation don't even notice it's there!
Seems logical, but verses also have a type such as "verse", "chorus", "bridge", "intro", "other" and "end". Maybe it's possible to add a feature to hide credits for verse types you can select, such as "intro" and "end"?