GPL License Question – Reusing User Interface?

Hi,

I have a license question.

I have read the GPL, and from what I understand, it says that if you use part of the code for another program and that it’s not distinct, then the whole program should have the same rights / conditions, that is, that it should be distributed freely.

I’d need some help clarifying this part.

What if i want to develop hosted service company ( software as a service ) and i’d like to get inspired from the admin user interface because it kicks ass so much ? ??

What would be the situation in the 2 following cases:

1 – The interface is similar visually, but a little different in terms of colors and small details, but the interface code is made by me from scratch. All the rest of the backend is mine and made from scratch?

2 – I would use the code form the interface, html, css and images, but all the rest and what drives the system is mine?

Would I need to make the WHOLE program available freely?
Would I need to make only the interface module available freely? ( what if it’s fully integrated with the entire system)?
Would it be sufficient to give proper credit and notice for the source of the work/code/inspiration?

Thanks
Peter