If you want to contribute to Cubyz, feel free to make an issue, pull request, or requests on other's people issues/pr.
You can start making an issue about the problem you're encountering or the feature, and if you can, and we encourage you, you can change the source code and make a pull request of the fix / addition, we will thanks you for that nicely done job. If you're doing that, you can do that more often please, it helps us a lot ! :D