I have the Poison Tail mold and Barlow's version is close but if you look at the gill plate cut on Barlow's, it is on the head. Do-Its head doesn't have that, the cut is way behind the head. Also I've spoken to Do-It many times, and they have always been very understanding. For instance all the jigs I sell, I use Do-Its molds and in speaking with them many years ago, they didn't have a problem with me calling their Poison Tail jig the same in my catalog. So maybe Barlows spoke to Do-It and got their approval. Also there is nothing that keeps you from modifying their mold and making jigs. On the original Poison Tail mold, if you are going to make permanent changes, fill in the back ring keeper with JB weld. Wait for JB weld to dry, sand smooth between mold halves, file your new bait keeper on the bottom of both mold halves and your done. Also you can use a 30º round bend hook in the Poison Tail mold as well.
Personally, I think a jig with a wire keeper holds the plastic trailer a lot better than a lead keeper.
Finally, I have seen a lot of people copy the Poison Tail mold, make changes and had a mold machined.