seamonkey: 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 CentOS possible default full paths are:

/usr/bin/seamonkey - from package: seamonkey

You may install the required package with command yum install {package}

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