What does “LD” and “MD” mean?
The LD tag stands for Line Dubbed, a term for pirate copies with an audio track, which has been ripped from the line out connection of a projector. Source
An example:
21.Jump.Street.2012.FRENCH.R5.LD.XViD-SERUM
The MD tag stands for Mic Dubbed. An example:
21.Jump.Street.R5.MD.German.XViD-CIS
Wikipedia articles explaining the situation in Germany:
http://de.wikipedia.org/wiki/Line_Dubbed
http://de.wikipedia.org/wiki/Mic_Dubbed