yabause-gtk: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/yabause-gtk - from package: yabause-gtk

You may install the required package with command apt-get install {package}

Error in other languages:
yabause-gtk: bevel nie gevind nie
yabause-gtk: comandă negăsită
yabause-gtk: comando não encontrado
yabause-gtk: commande introuvable
yabause-gtk: command not found
yabause-gtk: käsku ei ole
yabause-gtk: không tìm thấy lệnh
yabause-gtk: komanda nerasta
yabause-gtk: Kommando nicht gefunden.
yabause-gtk: kommandot finns inte
yabause-gtk: komut yok
yabause-gtk: nie znaleziono polecenia
yabause-gtk: níor aimsíodh an t-ordú
yabause-gtk: no se encontró la orden
yabause-gtk: no s'ha trobat l'ordre
yabause-gtk: opdracht niet gevonden
yabause-gtk: parancs nem található
yabause-gtk: perintah tidak ditemukan
yabause-gtk: príkaz nenájdený
yabause-gtk: příkaz nenalezen
yabause-gtk: команда не найдена
yabause-gtk: командата не е открита
yabause-gtk: 命令找不到
yabause-gtk: コマンドが見つかりません