Matt Legend Gemmell writing on Copycats:

There’s an entire spectrum of terms available besides ‘copied’, ranging from “inspired by” to “plagiarised”, and it’s not necessarily a bad thing to be influenced by the work of others. The key is to ensure that you’re consciously agreeing with a design, rather than just aping (mimicking unthinkingly - a definition which no doubt does our hairy cousins a grave disservice). Sadly, much of the technology sector simply apes.

His conclusion is perfect.

Innovation is about making things new, rather than necessarily making new things. To do that, you naturally need to know what things are already out there. No-one is saying you should design in a vacuum, and indeed you’ll never be able to anyway. Know the market, know your competition, and certainly live and breathe in the sector you’re designing for.