Hi
@ray_2204 The Substance Source downloads are only for the people who subscribe to Substance, our offer that allows people to always use the latest version of Substance Painter, Substance Designer and Substance B2M, and to have 30 downloads on Substance Source each month.
If you are interesting in getting access to Substance Source downloads you can subscribe to Substance for a short period of time, for example if you need 30 material downloads you can subscribe for a month.
The downloads do not decay even when you are not subscribing anymore, so you won't lose them if you unsubscribe.
There is no separate plan only for Substance Source.