This is the one thing that isn't as black & white as many think.
First, if the assets used are free use the user cannot claim those. If this dev made the assets themselves they can claim right to them. If they didn't they cannot.
Daz themselves offers limited licensing.
In some cases (AWAM fro example) the dev has made threats while they themselves have illegally used IP in their work. L&P used everything from Pink Floyd to GTAV in their work so good luck using anyone under the grounds of stolen IP/copyright.
The best and only real argument for copyright with a VN made with Daz and Renpy (freeware) in that of the writing itself. Yes, you would have to edit the previous words written as those are solely the developers.
Finally and most importantly, who are they going to sue? At best they could make a claim with Patreon or whatever payment/hosting company you used but...just don't take money for the work. Thay or use a company that doesn't care about any of that BS. There are options for that.
As for the sued user, good luck finding and suing a Chinese, Indian, British or whatever citizen for porn game IP theft when you aren't also in the country as the person that "stole" it.
In short, it can be done and there isn't a lot that can be done to stop it.
However, I don't advocate for that and even recently wrote that this dev should just sell it wholesale or for a monthly percentage to someone that wants to make it.
If that was refused, then I think it's fair to just continue it without them. They have no real recourse if the new dev did a bit of basic work to remain out of their reach.
