There is a special license that is for migration purposes only (like a Win XP to Win 7) migration, then the license would be timelimited, typically 6 months.
As with most of VMwares product this will be EULA-enforced, that basically means that there is no restriction in the license but you have to make sure that you have enough licenses to cover your usage.
The new licensing will be exposed with the next release of Mirage. (very soon)
// Linjo
