While designing my site I am constantly faced with the issue of whether its ok to TAKE ideas and designs from other sites. In some cases there is no distinction in certain aspec
I'm not a web developer, but I might have some insight that will help as well. My team has created several applications that have served as the starting point for other applications delivered to various customers.
The successful derivatives were those in which the developers took the time to learn the architecture and why things were the way they were. They then took the more crusty parts and rewrote them and in general expanded and improved the architecture.
Invariably, when a team simply took the existing project and tried to 'brand it' or copy it for a customer without actually figuring out the systems, they either created poor implementations of the extensions or had the project fail outright.
I realize this is a bit off the main topic of the ethical issues address by others here just fine, but my bottom line is that pure theft usually costs you more time than it saves.