It's free for everyone =D the majority of it will be implemented into Solace Crafting as well, except there will be material costs, etc. If Solace Builder itself evolves into a "game" meaning we get to the point of adding levels/quest/etc to it, then it may turn into a paid product, but likely the base version will always remain free, and gamification will be added as an upgrade package, similar to a cosmetics package.
Viewing post in will this be free for current owners of Solace Cragting?
So sorry for the response delay, sd1964, we've been grinding.
The builder will have a Steam demo release in August (likely mid-August, earlier if we can cut it but mid is the safest bet). Its actual release should be in October. So you can consider that integration into the main game should be in the Fall as well.