Forestall Chess

 In standard chess, it’s checkmate if you have no legal moves to prevent your king from being captured. In this variant, however, you lose if you cannot prevent an unavoidable checkmate on the next turn. This also means that any move leading directly to a guaranteed checkmate is prohibited.

So that it in principle plays just like normal chess? Sorry to be negative, but this is really pushing the definition of what a variant is....

It's normal chess except you can't play any move that gives your opponent mate in one

yeah, I understood it that way too. But you do not want to play such a moves, and there is not point in banning a kind of move you don't ever want to make anyway. It is just normal chess without small subset of blunders.
It would bring nothing new to the game, it is like making a variant where only change is that black goes first, or variant where new piece call tornado is where the knights normally are, but it still moves just like knight does.
It might be just me but I fail to see any reason to play this variant over normal chess. All that would happen is longer waiting time for a game followed by match with opponent who is less skill appropriate

Well normal chess is already kind of like that. If instead of checkmating the king, your goal were to capture it, the game would work the same except that there are more available blunders. The only actual difference is that stalemates can happen, adding some nice complexities to endgames. I'm not sure exactly how stalemates would work in this variant if you cant move into a mate in one position. But yeah it doesn't change the game much except for maybe slightly changing some endgame dynamics.

You're right, I think programming this is more funny then playing it instead of normal chess.