The Bella seat license authorizes use of the Bella GUI, CLI, and/or any desired plugin(s), on one machine, at any given time.
Licenses are not locked to any particular machine, nor to any particular operating system, allowing for hassle-free assignment of licenses to the various artists you may have in your organization.
Each license is perpetual for use, and also entitles you to updates at no charge, for a period of one year from the date of purchase. Licenses may be renewed at a 50% discount within 1 year from expiration, 25% discount within 2 years.
Additionally, note that the seat license includes 5 free node licenses, for rendering with Bella on up to 5 additional machines.