You mostly have two good options:
Upstream repositories and official Windows packages are handled by the core team, consisting of a bunch of people who are much trusted to keep Minetest progressing in good condition. The core team is best contacted on IRC at #minetest-dev @ Freenode.
The core team is formed of people who have made great contributions to Minetest.
Minetest is distributed as an engine, combined with a couple of games. Upstream repositories can be found at https://github.com/minetest/.
Games consist of mods that plug into the engine using the Modding API.