The most likely scenario is that very few people will look at your code, so it really doesn’t matter what you do with it. Harsh reality.
A slightly less likely scenario is that your project is of interest to niche academic researchers, and they’ll probably want to see your code and probably send you obnoxious emails. I wrote a little Ant Colony Simulation a few years ago and I still get emails from “phd students” doing Ant Colony Optimization (plz sir, help my thesis sir, plzz help plz plz). Although if you’re just putting it up on bitbucket, I’m not sure how they’ll even find it (I don’t really know what bitbucket is).
An even less likely scenario is that your game becomes popular enough to attract the attention of cloners. If it’s that popular, you’re going to get clones regardless of whether you release your source. However, if you can prove that somebody used your source (and it’s not under a license that allows that), then you at least have some way to fight them for copyright infringement.
The point is, I don’t really see a downside of releasing the source. Do you have a specific concern?