Lots of “source availible” licenses have a clause that a few years after development stops it becomes open source. Thing is, software with those clauses have existed for years now, and I dont know of a single case where it actually came into effect. Its very easy to have a minor patch every four years to prevent the license change, and if the devs of the software actually wanted to open source it, they would have done so whenever they wanted instead of only promising it. Clauses like that are supposed to combat abandonware, but abandonware does not usually happen because someone forgot the software existed, its a concious choice to not release the source.