When is a pattern modification really a new pattern?

At what point does a pattern modification become a whole new pattern?
The case in point for me right now is the February Ladies Sweater that has taken Ravelry by storm. What I have read about it so far gives a lot of credit for inspiration to the EZ SBJ.
But, it is obviously a new pattern, not just a derivation. Where does that line get crossed?
When did it become New and not Copy? Where is the line between the New FLS and something equally different that can stand on it's own merit?
The February Ladies Sweater is absolutely wonderful. When I saw it today for the first time, I knew that I would be casting on asap. The yarn has just been waiting for it since it jumped into my arms at the RenFest. A Black Baby Alpaca that is so luscious, I could not put it down. Of all the yarns there, this was far and away the softest. I would have picked it no matter what color it was.

There are literally hundreds of FLS photos posted on Ravelry. Many, many of these are being made as fast as needles can fly. Very few of them are in dark shades. Maybe because of the season of the year. Maybe because black doesn't photograph well. And, I agree that the FLS does look lovely in all of the infinite varieties of colors and fibers out there. But, I have this black that is begging to be made into something that I will want to wear every day.

Modifications:
1) The baby Alpaca is far finer than what is specified, worsted, I'll check exactly how fine.
2) The square neck isn't the best for my narrow, slopey shoulders. I'll be checking into a smaller, rounder neckline.
3) The widening look at the shoulders is good, and I'll be emphasizing that as much as possible.
4) Maybe not so much garter stitch. The Baby Alpaca wants to be smoother than all garter.
5) The lengthening look of the vertical lace pattern is good, but I'm not sold on the pointy shape of the lace. Due to the yarn's RenFest background, it wants to be a celtic knotwork of some kind. Aran or Gansey or some such mystery.
6) Not so sure about the 3/4 sleeves. Not sure why, I always push my sleeves up to that level anyway, so why not start out there? Hmmmmm
7) Must have a pocket somewhere. Yeah, I'm weird.
8) Not so sure about the baby doll, show off the baby bump effect on someone of my age. Might be kind of scarry.
9) Will be as long as I have yarn to make. It could end up quite a lot longer than in the design. I knit until the yarn is gone. Yeah, I'm weird.

So, more planning, more sketching, more thinking. Maybe if I just hold the yarn for a few minutes it will tell me what it wants to be.