This feature is available in all editions.
You can invite guest collaborators (non-Lifecycle members) to participate in any conversation.
Type an email address in the Mention field, and then select Invite Guest Collaborator. The guest collaborator will receive an email message with a link to register.
After registering, they can participate in the conversation stream.
Note that guest collaborators do not have access to any projects or assets in the system. They only have access to conversations where they're mentioned. If they're part of a conversation where someone has mentioned a secured asset, the guest collaborator will see the conversation, but not the mentioned asset.
Member and System Administrators can promote a guest collaborator to a fully licensed member. They can also deactivate guest collaborators.