The VMware Single-Processor Licensing Policy clarifies the licensing of VMware ESX and VMware Infrastructure Suites (VI).
Customers may install VMware ESX and VI licenses on single-processor physical hosts that are included on VMware's Hardware Compatibility List. This policy applies to servers with two sockets that are populated with a single-processor. Each processor may contain up to six cores. Please note that licenses for VMware ESX and VI are still sold in minimum increments of two processors. With this policy, VMware is clarifying that a two processor license may now be split and used on two single-processor physical hosts.
To install licenses in single-processor increments, you must use the Centralized License Server model for generating and managing VMware license files, as described in the Help page for Create License File – Select Licensing Model. With this licensing model, a single license file holding your licenses is stored on a license server. The license server manages an entire license pool, making licenses available to one or more hosts.