This tab is only available for Company Blueprints.
The default option is set to Do not share
If you have a related company you want to share Blueprints with, you can click Selected Companies
(You will need to enter the ID of the Company taken from Admin > Configuration > Company Preferences > Sharing ID)
The Marketplace option will share Blueprints with ALL companies.
This option is more suited to Hydra to share demo blueprints and would not typically be used by a customer.
The marketplace option is visible to other companies via Blueprints > Company Blueprints > Blueprints List using More Options