DPOS seems to refer to completely two different things.

Firstly, there is BitShares' DPOS system which stands for "delegated proof of stake". This is the most common meaning of "DPOS" and is the one that most people probably think of and are referring to:

http://wiki.bitshares.org/index.php/DPOS_or_Delegated_Proof_of_Stake

Then there is also something called "dynamic POS" which OP mentioned. Dynamic proof of stake (also called DPOS) seems to be a variant of proof of stake used by the lesser known altcoins Positron and Isotope. I'm not sure how it differs from traditional POS but it looks like it involves stake rewards which change over time depending on which blocks are mined:

http://bitcointalk.org/index.php?topic=1021029
http://bitcointalk.org/index.php?topic=1039891