Employed an open beta phase at some point, allowing anyone to play the unfinished game for free for a time before release. Usually in hopes of stomping out all remaining technical issues but possibly also for marketing.
The first video game about Open beta was released on December 1, 2009.
This is also as opposed to closed beta where only people with invite, pre-purchase, press access, or similar could play it.
Sometimes claimed to be an excuse to release a buggy game, as microtransactions are often enabled at this point and not all games bother ever getting "out" of open beta.