The perpetual licensing model, where you would pay a one time fee for the software and own that version forever, has been rapidly declining. The dominant model today is where the customer pays a recurring fee. This could be per user or per tier for a given term.
Microsoft's tussle with UK-based reseller ValueLicensing over the sale of secondhand licenses returns to the UK's Competition Appeal Tribunal this week, with the Windows behemoth now claiming that selling pre-owned Office and Windows software is unlawful. ValueLicensing's representatives say this week's trial - due to start tomorrow - will "address whether the entire pre-owned license market was lawful - with Microsoft arguing that it was not lawful to resell pre-owned Office and Windows software at all."