All code of the whole Melinda framework is available here (INRIA code hosting service) : the "SCM" section tells you how to fork the repo, the code itself can be browsed by clicking "browse git repository" on the right. Feel free to clone the git repository and send us your pull requests. As well, feel free to fork the project or any of its part : if you do so please show us your work ! For more detailed informations about the code, read on.
Melinda keys extraction tool's java code is available on the repo as well. This project (the web API) is really extremely tight to it so there are great chances that if you want to modify, change or add feature to this project you will have to modify its code as well. More informations about the keys extraction tool can be found here (INRIA forge project's wiki).
The web API is written in Python using Django web framework and also a lot of Django REST framework as well. The project is open source and is part of the overall Melinda framework so the code is also here (still INRIA code hosting service). If you browse the repo you will find the web API code in tree/trunk/melinda_wi. In the "docs" folder there are a bunch of document describing several things :
We also recommand you to read the README.md in melinda_wi's root which gives you a general overview of the code so you will not lose yourself in it.