Since the haggler helps you? It's not legit. But it's safe. Have never been frozen for any GM haggler
As for the script,'it's from a legit coder. Not sure if it is current and updated. By the way, I think manual haggling and clicking miiiiiiiight be faster if you're good and if your GM script lags
I find haggling manually is better, once you get used to it, it's cake, if anything, I would say adblock restock.
It only haggles?, or also buys the item? Nevertheless both of them have low freeze rate if used in the correct shops. I mean, do not use them at highly profitable shops like magic shop..use them on books, food, etc