0 A.D. is an epic free and open source real-time strategy game.
You don’t have to pay for 0 A.D. These downloads are completely legal.
About this post
As explained in a recent news post by the 0 A.D. team, You Do Not Need to Buy 0 A.D. on eBay.
It would be ideal if the teams behind open source projects would have people working on selling the game in an ethical way that would support their work and the people working on the project.
Ethical would for example mean that it would be clearly stated that the game can be downloaded for free, what kind of physical box to expect (if at all, I remember that SuperTuxKart would often be sold as a “digital download” product) and laying out the distribution of income transparently. This would turn the purchase into a donation (whether that is an acceptable word to describe it needs to be checked with eBay terms) and there are likely to still be buyers that don’t have the skills or time to read the text or double-check the freeware status of the game or only look at the screenshots.