fit_spline_dfield: 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

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/lib/cmtk/bin/fit_spline_dfield - from package: cmtk

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