Bitcoin was fully implemented by the same person (Satoshi Nakamoto) who in large part designed it (based on pre-genesis research by Adam Back, Wei Dai, David Chaum, and Nick Szabo, among others). For this reason, a single “Bitcoin Whitepaper” exists. In contrast, Namecoin was implemented by a developer (Vincent Durham) who had no prior involvement in the design (he just did a code-drop). As such, there is no single “Namecoin whitepaper”, as Namecoin’s design is not attributable to a single person. There do, however, exist several whitepaper-ish documents by pre-genesis researchers. These are the closest things to a “Namecoin whitepaper” that exist.