I think this is the easiest thing to do. I could follow what contributors do on github, as well as on the blockchain through the associated posts that may be written.
On your personal side, you can create a github account and create one new project in there, that will contain your contribution to the MadAnalysis public analysis database. Since this corresponds to the only files you will modify (actually create) by yourself, it is fine (you will not have to touch madanalysis 5 itself, but only an external file that will be used by the platform for physics (if successfully coded at the end of the day).
I hope this clarifies :)