Back in February, it was revealed that Starbreeze's year-end financial report included mention of PayDay 3 being in full production. The developer in question, Overkill, has been working on the game since then. They made the slightly inflammatory statement that they would release PayDay 3 in good time. That they would put the game out when it was ready. In doing so they were seemingly attempting to take any pressure of an announced release date off of their plate so that they could make the game the way they wanted to.
Well it would appear that mindset has continued into their currently released game, PayDay 2. The game has been released since 2013 but still has a fairly active player base. PayDay 2 also recently received an Ultimate Edition Update. To celebrate, Overkill has released the game for free through Steam. It's only free for the first five million accounts, though.
It's clear through the comments on Steam that some people are already using multiple accounts to get many copies of the game. So time is of the essence! If you and your friends want to get PayDay 2 for free to play together, do it as soon as possible.
Source: PayDay 2 Steam Community