Tony Robbins and Brian Tracey worked together for awhile as far as I know. If you look at some of Tracey's development material, it looks a lot like Tony Robbin's. I'm not saying Brian took from Tony.
I think it comes down to interpretation. If you use your own interpretation then I think you may be safe. But there is always a fine line. But there are principles that are simply universal and cannot be copy-writed. The golden rule is probably the most known. I think any personal development guru may follow many of the same lines of principality.