DF vectors are "deleted foamy" virus vectors that only retain essential cis-acting viral sequences. The four plasmids requried to make DF vectors are pCiES, pCiGSDY, pCiPS and pDF. The first three plasmids are helper constructs expressing Env, Gag, and Pol respectively. pDF is a deleted foamy vector backbone with a polylinker for you to insert a transgene cassette. A description of the plasmids (Trobridge et al., 2002). Note however, that pCiGSDY os a newer version of the pCiGS Gag expression plasmid described in that paper, with a more complete deletion in the packaging signal (Josephson et al., 2004). All the plasmids encode ampicillin resistance.
For more information on foamy virus vectors see refernces below. See separate links for an FV Vector Production Protocol and the seuqences of plasmids.