Log in to BIMcloud is tied to the licensing - when one is signed in, they acquire a license and keep it up until they sign out.
In this case you either need to have some extra licenses available for your contractors, or in case of BIMcloud SaaS you can invite contractors with their Graphisoft ID and configure their users to use only their borrowed license from their own tenant.
That's Huge disappointment, That puts the use of BIMcloud server for documentation almost useless as there's no way that hundreds of involved people will buy costly Licenses to share documents through BIMcloud server.
So BIMcloud server wisely can be used only for Archicad in-team users but not for even minimal, limited CDE needs.
You are right, BIMcloud is a collaborative design solution, but unfortunately, it is not a Common Data Environment (CDE) and does not offer functionalities that most common CDE applications offer as it is not its intended use case.
Of course, you can always post wishes about it if you need such a functionality.
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