Can I share material with a third party without granting them full access to a production?

Yes, you can make a shared link and send it to your colleagues. With this link they can access a collection in a production without creating a Limecraft account.  

The collection can be shared with anyone (also people not part of your Limecraft Flow production team). Click ‘Share Collection’ and click ‘Generate Shareable Link’ to get a link for your collection. This link can be used in e-mails, chat messages and so on to give the receiver access to the clips in your collection.