morseX11: command not found

Have You tried accessing the binary with the full path?

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/morseX11 - from package: morse

You may install the required package with command apt-get install {package}
Error in other languages:
morseX11: bevel nie gevind nie
morseX11: comandă negăsită
morseX11: comando não encontrado
morseX11: commande introuvable
morseX11: command not found
morseX11: käsku ei ole
morseX11: không tìm thấy lệnh
morseX11: komanda nerasta
morseX11: Kommando nicht gefunden.
morseX11: kommandot finns inte
morseX11: komut yok
morseX11: nie znaleziono polecenia
morseX11: níor aimsíodh an t-ordú
morseX11: no se encontró la orden
morseX11: no s'ha trobat l'ordre
morseX11: opdracht niet gevonden
morseX11: parancs nem található
morseX11: perintah tidak ditemukan
morseX11: príkaz nenájdený
morseX11: příkaz nenalezen
morseX11: команда не найдена
morseX11: командата не е открита
morseX11: 命令找不到
morseX11: コマンドが見つかりません