commercial

Hello,
Because GNU License doesn't say it clearly, can i use Drupal to build sites and then sell them and if yes what are my legal restrictions?

I'm seeking some advice around licensing for my software and Drupal. Thanks in advance to those who offer their opinion!

1.) I created and own a standalone, commercial, script. It can run as a php web application in its own right (no linking to any 3rd party software).