tkmelting: 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/tkmelting - from package: melting-gui

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

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