Do you even need to ask?
Of course there would be interest in a open source DF.
The only problem is such a thing is more or less impossible, because of the amount of work required. The problem with most open source projects is that you have to take the first step yourself. Given the sheer size of this project, you are going to have to do a lot of coding before you can spark (real)interest and engagement of other programmers/contributors. In most cases you are going to be the one who will be pushing the project forward. This is how it goes with these kinds of projects.
If you are still interested in starting this project. Start by making a parser for game data files. This will be a huuuuge undertaking considering what a huge mess of different tags there exists by now. Keep in mind DF has been in development for many years, I would not be surprised if even Toady would not have a clear overview.
Secondly, you would have to reverse engineer probably a huge mess of magic numbers and equations that eventually creep in during the development of such a massive procedural beast that is the dwarf fortress game.
Then there is the game itself.. Well, that is a whole other dimension of magnitude that will require an even enormous effort.
Alternatively you can make a DF clone.
It's been attempted many times with varying degrees of success. Good luck.