dave: 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/dave - from package: libhttp-dav-perl

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

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