You need to have some significant differences to avoid any infringement. Woodworkers often copy other peoples ideas and many do not have patent, copyright or trademark protection. The reason for that is it costs big bucks to get. This is why you see so many copies of Bob Rosendahls designs. Bob's box joint jigs, miter sled and EZ Link Systems are showing up everywhere these days with minor modifications. It is a good thing they are since Oak Park is selling off remaining inventory and not producing more at this time.
"Living in the D" (this means Detroit!)
"It's fine to disagree with other members as long as you respect their opinions"