What is the difference between pricing model of v4.0 and v3.x?
When you buy v3.x, you can get free upgrades to minor upgrade e.g. v3.1, v3.2 but not major upgrade e.g. v4.0. 3 months grace period is given to free major upgrade for customers bought within 3 months before release of major upgrade (v4.0 was released on 12 Aug 2006). In v4.0, 1 year subscription of free upgrades regardless of minor or major was introduced. 1 year upgrade subscription protects your right to get free upgrades within 1 year.