Michael Baierl wrote:
If I remember the GPL correctly you can do that - just use Roundcube (or any other GPLed software) and make changes to it. If you sell the software you have to also release the changes. Freedom to use it.
Finally I found an example - 1blu, a hosting company located in Germany, is using Roundcube: https://webmail.1blu.de/
Some screens (German) can be found in their help system: http://faq.1blu.de/index.php?action=artikel&cat=127&id=222&artlang=de
They removed the copyright notice (better: the powered by notice), but the copyright still belongs to Roundcube.
Mike