Hi Juan!
Basically most stuff of the Substance stack will remain MIT (Document, Article, Data, Operator, Chronicle, Surface, Reader), except everything related to editing, which will supposedly all live in a new substance/editor repository (not ready yet). The editor project will provide a general-purpose toolkit for realizing web-based editing scenarios and will be bare-GPL licensed. We'll give away commercial licenses individually on request. If your project is in a non-commerical context we can get you a license for free (e.g. for integrating the editor into your MIT-licensed project). Just ask. :)
We are not open sourcing the Substance Composer, as this piece is dedicated to the consumer market and shipped as desktop application. However there will be general purpose integrations of the editor that developers can use as a starting point.
Cheers, Michael