Complex sentence: Valve began allowing developers to use these advanced features in January 2015; the developer and content generator will share the profits of the sale of these items; the feature went live in April 2015, starting with various mods for "Skyrim".
Split into simpler sentences: Valve began allowing developers to use these advanced features in January 2015. Three months after Valve had announced in January 2015 that the developer and content generator would share the profits of the sale of these items, this feature went live in April 2015, starting with various mods for "Skyrim".