I would guess Other World Mapper which is first on this page of the thread and has a demo and the purchase is "limited to one year". Except that it's not a one year limitation exactly. The download in the email expires after one year but assuming you've downloaded it, you can keep using it for as long as you would like. They also email you a fresh download link with all of the new versions. I assume this is in place so that if it moves forward to version 2, a significant version improvement over 1.2, 1.3, 1.4 etc, like Affinity did, they can charge you for that one. It's also cross-platform, Linux and Mac and Windows. So it fits the description of the comment.