Better to cite github project or web page of unpublished software?
As a reader, I would find a citation or mention of both resource types to be useful, especially in the all-too-common event of a link breaking or a github project going dormant. If you're concerned about formality then contacting the original authors to determine which citation they would prefer would be helpful. Otherwise, as long as your audience knows what you're referencing and where to find out more about it, you should be fine.