Usually "2.0 surround" is encoded in Dolby Surround, but there are compatible alternative (read: when decoded with a Dolby Surround decoder they will sound as good as the original DS material).
The ones you could find on laserdisc are DTS Stereo, UltraStereo, CHACE. And, IIRC, there were some company that avoided to pay Dolby royalties, so they decided to print on the cover only the words "Surround Sound", without Dolby... don't know if the track was mixed with a Dolby encoder or with another method.
DPL - Dolby Pro Logic - is a decoder, that decoded Dolby Surround encoded material; there is no DPL encoded soundtracks.