Keen Software House has released the source code for Space Engineers, offering support for modifying the indie space simulation. This announcement has the news, while a developer's blog offers more details on the plan, including how they have set aside $100K to further bolster mod development. It sounds like they are remaining flexible in how this is disbursed:

To support our modding community even more, we reserved $100,000 of our own money as a fund for modders who want to build total conversion mods based on Space Engineers or VRAGE engine.

We’re considering several ways how this fund could work: grants with no strings attached (see how Epic does it with UDK – https://www.unrealengine.com/unrealdevgrants), zero interest loans and Kickstarter support. We can provide PR, marketing and promotion on our social media.