What this likely means is that the engineers at Square get some kind of vesting stock options (i.e. golden handcuffs) that are valued in aggregate at less than

What this likely means is that the engineers at Square get some kind of vesting stock options (i.e. golden handcuffs) that are valued in aggregate at less than $3 million. It also means the engineers get to have a well-recognized brand on their resume, and not a gap of a few weeks to months that then needs to be explained (not to mention the hit their bank accounts would take). This is generally what's called an "acquihire."