GNU/GPL and Attribution

[Bobbi Anderson]

We are looking to create an Open Source project for a system that provides
easy creation of integrated web-based tools for use by web
designers/developers. We would really like to use The GNU General Public
License (GPL) for this.

We are quite comfortable with hosting companies taking this free code and
offering it to the web designers/developers that are hosting with them.
However, we would like those designers/developers to see an attribution to
our company. 

So my question is, will the GNU/GPL license cover this attribution need? If
not, is there a copyleft license that will incorporate our needs?  If not,
can we just add a paragraph about attribution on our website, or in the
GNU/GPL license?  Or, will we need to write a whole new license?

Thank you so much for your attention,

Bobbi 

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