Up until now I hadn't really looked into the more obscure Mega Drive pirates, mostly the ones with Chinese names. I recently found this (and credits to Taizou for the video)
http://www.youtube.com/watch?v=480UnEPhxIA and I noticed that the music in this game is reused in other pirates. The boss theme is remixed for that Mortal Kombat Mythologies game on the Mega Drive and the ending theme is reused for the 3rd level of that game, the second level of Pocket Monster and KoF99. From searching around, I've found that the first level theme is reused in KoF99 as well and the theme for the second level is reused in Mulan and MK5 so I think we can assume that all of the pirates that use the same sound engine (High Seas Havoc's engine, if I recall) are by Never Ending Soft Team. I'm sure there's some other tunes I missed but I think that's proof enough.
Thing is though, if all of those games are by them then who are DVS Electronic Co., the people who apparently did the Super Famicom port of Pocket Monster? Are they another company that Never Ending told them to do ports for, or were they just an alias? Kind of confusing seeing as the music in some of the games is completely different. (and in the case of Pocket Monster, stolen from Bonkers on the SNES) Not to mention, the engines seem to be recoded from scratch as opposed to being a regular port.