As a brief introduction, I want to emphasize several points from my own understanding:
Do you really need Madagascar? Yes because you will benefit a lot from it. Of course no if you are able to manage things in your own way, even better than Madagascar.
Assuming we need Madagascar hereafter. In what aspects we can benefit from it?
Is it a responsibility to contribute your papers, in particular your codes? Definitely no, especially when your research is sponsored by others while a permission public release is not accessible. You may want to be selfish: ``I only want to use the codes from others instead of sharing mine with the community''. No objection: Some people are doing things like that.
Keep in mind Madagascar is not the goal, it is just a tool to share your research progress with others. If you are ready to be open, why not a contributor?
From modeling to full waveform inversion: A hands-on tour using Madagascar