Datto's licensed commercial implementation of owncloud.
At time of writing, you can add clients to Datto Drive and they'll get 1 year for free of the 1TB plan. After that it's $10/month. Partners get 1TB of storage for free forever.
Datto Drive is similar to Dropbox, however for $10/month you get 1TB with unlimited users. You can have a company with 120 employees and if you only need 1TB of storage across all of the employees then you can use the $10/month plan. Each user's documents are private and they can share files and folders with other Datto Drive Users, Groups, or even outside people.