KnowledgeOS is free to use forever. You can use the basics, including tab management, search, history tagging, basic collaboration, etc. as much as you want.
Comake also offers you premium services (and Knowledge Apps) that can be added (or installed) over KnowledgeOS. These services are focused on helping you manage your Knowledge across Apps, people, devices, and time. Below is a brief overview of the first premium offerings over KnowledgeOS.
Back up my Knowledge to Comake Cloud and sync it across devices
Manage all of the data across all my Apps and Accounts using KnowledgeOS
Advanced collaboration and people management within workspaces.