Stranded means you have no means for moving from where you are, or really no practical/acceptable means (you could swim off a deserted island for instance, but that probably wouldn't be considered a practical means of moving off the island).
Boeing has stranded these astronauts on the ISS because it has no (acceptable) means of bringing them down, and the astronauts themselves have no personal means for doing so. If they want to become un-stranded then somebody will need to arrange the means for them to come down.
That doesn't mean that it's impossible for somebody else to provide those means, or that the means simply don't exist in any capacity. But they meet both the dictionary and common colloquial definition of stranded.
Boeing has stranded these astronauts on the ISS because it has no (acceptable) means of bringing them down, and the astronauts themselves have no personal means for doing so. If they want to become un-stranded then somebody will need to arrange the means for them to come down.
That doesn't mean that it's impossible for somebody else to provide those means, or that the means simply don't exist in any capacity. But they meet both the dictionary and common colloquial definition of stranded.