Danland theme license I have chosen the Danland theme for my drupal site.
The theme is licensed as GPL (from the license attached to theme). At the bottom of the theme on my website, there's "Theme by Danetsoft and Danang Probo Sayekti inspired by Maksimer", and I'd like to ask you if I can remove it (I won't derive and publish the theme).

I think I can, but I'm not sure.
Any module/theme hosted on Drupal.org is licensed under the GPL License v2+, which allows you to edit them, as long as you respect the license itself.

You can edit out that string. Even if you were distributing your version, you should distribute the source code too, which is the theme itself, as PHP is not compiled. You should not remove the attributions left in the comments from the previous author, though.