We just completed developing a web app for a client. And like i usually do, i added developed by "My Company" at the footer at a very small insignificat size. I sent the client an Eend user license stating some of the following in summary

you can't resell, redistribute, etc without our notice
...
you can remove the attribution or design credits

the client got back to me and complained, telling me now that he was also developing for someone, and that 'I can't add my attribution' without his/her consent, but?

Although i sign a NDA with in summary states that i cannot disclose the software to anyone else

There was no agreement before the project that am not to add design credits or attribution

i know every software i install have that, and so is every products from companies, mostly technological products.

how does this work (adding design credits) What do you think?