Just updated it!
Why didn't you share the URL to sign up in the article
OMG! this is awesome!
You’ll get a chance to view how Allegorithmic created materials from the Substance Source library. Make adjustments to the graph and the nodes to get different variations.
The idea behind releasing the .sbs files in Substance Source is that texture designers should not be limited by the presets available within the .sbsar files. The graph’s fully adaptive structure gives you the opportunity to make any changes and transformations you need beyond the original setups. From modification of a few nodes to making new textures from a graph template, you don’t have to create new materials from scratch.
You can find more on the open source initiative here.