Why is gog hosting an illegal title?
https://talkchess.com/viewtopic.php?t=42465

Maybe because it is not illegal?
I am not a lawyer, but I don't see any copyright infringments except the naming (which
I would think is ok ... as I am no lawyer).
Actually there is no use of neither copyrighted code nor art - as far as it was reported.
The lawsuit was just for the US and only there it could be a problem ...
and it was sold in North America with the name "Check vs. Mate" underpinning the fact
that the name was in trouble - not the game itself.
So this is setteled and no problem.

While I know about a lot of stolen code (of well known companies), this seems
to be more about advertising and trademarks ... and does not go deep.
One may start with the Wikipedia entry here:
* https://en.wikipedia.org/wiki/Battle_Chess#Inspired_games

Additionally, the lawsuit was risen due to its new game (available on the dark side):
* https://store.steampowered.com/app/200150/Battle_Chess_Game_of_Kings/
and I don't think that this can compete with "Battle vs. Chess" in any respect.
On steam it is Mixed (351) - which is extremely bad for Steam.
Especially as they just have thumb up or down ... but it is the US way of living ... ;)
And compared to Mostly Positive (650) for "Battle vs. Chess" on Steam.
So Steam sells it, too ... and this is USA! :))

But one may judge about quality in comparison - e.g. via a video here:
* https://www.youtube.com/watch?v=pwqAtNquu1A
and compare it with the videos on GOG about Battle vs. Chess.