While there are the usual legal bizzarities ( http://blog.smartbear.com/apis/api-copyright-and-why-you-should-care/ http://blog.smartbear.com/apis/api-copyright

While there are the usual legal bizzarities ( http://blog.smartbear.com/apis/api-copyright-and-why-you-should-care/ http://blog.smartbear.com/apis/api-copyright-and-why-you-sho... ), there's no reason this should be any different than copyright of code. Design-inspired is not design infringement.