Hey! The official Factorio mods app is up and running!
Stop using this one and go to http://mods.factorio.com
This app will be decomissioned soon! Thanks for your support!

How to create mods

Factorio mods are created in the LUA programming language. You can follow the modding tutorial on the Wiki.

After you create the mod, you should publish it to the official Factorio mods subforum.

And it's encouraged to release the source on Github! Github also allows you host zipped releases!