Patents
micks56: The short answer to how close you can be is you don't know till you end up in court. Now, for the longer explanation.The Supreme Court of the US has ruled that patents can be obtained for "anything under the sun." Exceptions carved out by the same court are for laws of nature, maths, and abstract ideas.So you can't patent F=ma, but things in web e-mail clients could be patented.There is no way to tell if you are infringing without actually reading the patent claims. So until the patents are granted, you don't have anything to analyze.Also, their patented claims do not have to be identical to what you are doing. If it is obvious to someone skilled in the art that what you are doing is a modification of what your competitor is doing, then that could also be infringement. This is why you see the language "in one embodiment" in patents. The drafters are not limiting themselves to the claimed implementation, but are trying to do a land grab that people skilled in the art would do after reading this application.In legalese this is called the doctrine of equivalents. The United States section on the wikipedia page for doctrine of equivalents is currently accurate. You will see the standard there.