VMware just released the vSphere 5.x licensing details.

When I originally created this post, I was mistaken, and had a good deal of inaccurate information. In the interest of clarifying the vSphere 5.x licensing information, here are some excerpts from the PDF linked to above:

vSphere 5.0 licensing removes all restrictions on physical cores

and physical RAM

We have introduced vRAM, a transferable, virtualization-based

entitlement to offer customers the greatest flexibility for vSphere

configuration and usage. vRAM is defined as the virtual memory

configured to virtual machines. When a virtual machine is created,

it is configured with a certain amount of virtual memory (vRAM)

available to the virtual machine. Depending on the edition, each

vSphere 5.0-CPU license provides a certain vRAM capacity

entitlement. When the virtual machine is powered on, the vRAM

configured for that virtual machine counts against the total vRAM

entitled to the user. There are no restrictions on how vRAM capacity

can be distributed among virtual machines: a customer can

configure many small virtual machines or one large virtual machine.

The entitled vRAM is a fungible resource configured to meet

customer workload requirements.

vRAM entitlements can be shared among multiple

hosts. There are no restrictions on how vRAM is consumed

across virtual machines and CPUs. At any given point in time,

the amount of vRAM consumed by active virtual machines on

a CPU could exceed the base entitlement of the vSphere 5.0

license assigned to that CPU. As long as the total consumed

vRAM across all virtual machines managed by a VMware vCenter

instance or multiple linked VMware vCenter instances is less or

equal to the total available vRAM, vSphere is correctly licensed.

Creating the vRAM Pool

For this example, a user has two 2-CPU hosts that they wish to

license with vSphere Enterprise edition. Note that the vRAM

entitlement for vSphere Enterprise is 32GB per CPU. Each physical

CPU requires a license, so a minimum of four vSphere Enterprise

licenses are required. More licenses will be required if the user needs

to use more vRAM than the 4 x 32GB = 128GB of vRAM that is

entitled with the four licenses. So far the user has yet to create any

virtual machines, so 128GB of vRAM is more than adequate. In sum,

the user purchases and deploys four licenses of vSphere Enterprise,

yielding a vRAM capacity of 128GB of vRAM