In previous versions of Coppermine the "Powered by Coppermine" used to be obfuscated to make it hard for non-coders to remove the tag. The reason behind this was an additional license add-on that disallowed users to change the line. The dev team has reviewed this policy for cpg1.5.x and decided that end users are allowed to change or remove the line in legal terms - for details, please review the Copyright & Disclaimer-section of the documentation.
However: We have a forum policy for the support board instead: support will only be given for galleries that show the "Powered by Coppermine" tag unobfuscated.
Before removing the credits, please consider this as well: Coppermine is free software, the dev team asks you to keep the footer intact. We're convinced that you should give credit where credit is due. Additionally, the footer is meant to spread the word about Coppermine, with the "Powered by Coppermine"-tag giving others the opportunity to get a gallery of their own. So please think twice before you decide to remove the tag.
This being said, this is how you can change the tag: to edit the place where the tag is being displayed, edit themes/yourtheme/template.html and move the placeholder {CREDITS} around. If you remove it from themes/yourtheme/template.html, the original default tag will show through. As it is being generated by Coppermine's pagefooter function, it needs to appear below the {GALLERY}-token. To change the content of the disclaimer, edit themes/yourtheme/theme.php and edit the function theme_credits as you see fit. If this function doesn't exist in your custom theme, copy it from the sample theme into your custom theme first. To actually remove the "Powered by Coppermine"-footer completely from the output, just modify that function to output nothing.
Instead of removing reference to the Coppermine web page completely, we encourage you to edit the function in your custom theme and add the information you would like to see. Here are some examples for the output of what the Coppermine dev team considers to be fair use: