Can JumpCloud replace Active Directory?

Yes, it can. Like %90+ of companies, you don't need the complexities of AD.

For the most part, Jumpcloud can replace Active Directory if your Active Directory requirements are relatively basic. For example, Jumpcloud only supports a subset of Group Policy settings. You can't set group policies for automatically sharing network folders depending on user or user group, or automatically install printer drivers for new users or devices. If you have an all Microsoft environment, a DC with Active Directory is more robust with more granular control. However, if you have a mixed environment (PC's., Macs, Linux) and do not need the more advanced features of a DC and Active directory, then Jumpcloud is likely going to be a better option. Junpdrive does provide for integration with and synching with Active directory though.

Yes it can. We have clients that are very geographically distributed and we use JumpCloud instead of AD for these clients.