(I guess is japanese) I thought it was some bug at the beginning but now I think it was just changed permanently.
Any reason? Lure japanese people to a 99.999% english forum?
To restore the original one just add:
document.getElementById("site-logo").src = "https://arduboy.com/b/wp-content/uploads/2017/02/arduboy-title.png"
To a tampermonkey script.