Now I want to know, is it okay for people to try to continue where the dev left off and try to finish it or would that be consider stealing that person work?
The game is obviously the entire property of its original creator, what mean that it would be stealing, but this is just the legal aspect of the issue.
To continue a game, you need to know how its story is supposed to evolve and finish, in order to keep it coherent. You need to be able to write with the same style than it is wrote, to not break the continuity. You need to be able to draw like the original creator, for 2D, or to have all the assets the original creator have, for 3D, or to know all the preset used, for Illusion studios, for the characters and locations to stay the same.
In short, if you've the talent need to actually continue an abandoned game without turning it into a big mess that worth nothing, you've also the talent to starts a game all by yourself, what would be way better.