The Bella node license authorizes rendering with Bella on one machine per license, at any given time.
Licenses are not locked to any particular machine, nor to any particular operating system, allowing for hassle-free network/farm deployment.
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.
NOTE: the seat license includes 5 free node licenses, so take care not to purchase node licenses unnecessarily, if you are also purchasing a seat license.