Commercial CodeIgniter

[eluser]zaussome[/eluser]
Hello,

I'm aware that CodeIgniter is open-source software, but recently one of my clients has risen that it's illegal to sell an application built using a framework without a public domain license.

I'm not too sure about the law on this or if CI allows it, could I get some input from a experienced user?

Thanks,

Devlin

To clarify, I'm not selling CodeIgniter or a modified version of it; I'm using the standard version for it's standard use on a website that was built for a client.