Solução: instalado a partir do pacote AIX, não do RPM:
0:root@SERVER:/root # lslpp -L | grep -i samba
samba.base 3.0.24.0 C F Samba for AIX
0:root@SERVER:/root # which smbclient
/usr/bin/smbclient
0:root@SERVER:/root # lslpp -w /usr/bin/smbclient
File Fileset Type
----------------------------------------------------------------------------
/usr/bin/smbclient samba.base File
0:root@SERVER:/root #