I seem to recall hearing the term "obstacle DP" before, but I don't know where I heard it. I have not seen it printed on anything though, so maybe it's an unofficial term?
I have a guess though. Is it possible this term refers to the non-standard takeoff procedures (like Jetguy said)? I am thinking of the "T" printed in a black triangle on the bottom of NOS plates. This refers you to a page that describes an IFR takeoff procedure.
For example, I departed IFR out of Williamsport, PA once (KIPT) from rwy 9 in IMC. Though there is not a published DP with a name (as would have been called a SID in the past, like REDSS FIVE out of CVG), there is a procedure listed. I don't have a copy with me now, but the procedure called for runway heading departure to something like 2500 MSL, then a climing left turn to a VOR before proceding on course. The reason for this procedure is to keep you away from the 2000 ft. mountain ridge on the south side of the airport.
My guess is that procedures like the one I described above are what some call "obstacle DP's". They were created to keep you from hitting something (just like a published DP with a name), but were not invented because of a need to organize departing traffic from a busy airport.
Hope this helps!