I'm a little confused as to who made what game.

Looking on my BG2 box, I see Bioware, Black Isle and Interplay logos. Who made the games?

BG
BG2
IWD
NWN

Am I correct to say Bioware made BG, BG2 and working in NWN while Interplay made IWD?

If that is the case, why does Interplay have their logo on the BG and BG2 boxes?

Syl...

Well the short answer is yes. The real answer is all of them have some part in all the games you listed (BG, BG2, IWD, NWN). To start with Interplay is a publisher. They product the game. It's like when you buy a book, some big company puts up the money for printing and distribution. Black Isle is a division of Interplay that specializes in RPG games. And Bioware are the people who 'really' make the games. The authors if you would. I hope that helps.

BG - Totally Bioware
BG2 - Totally Bioware
IWD - Black Isle, used Bioware's Infinity Engine from Baldur's Gate
PS:T - Black Isle, used Bioware's Infinity Engine from Baldur's Gate
NWN - Totally Bioware

Both IWD and PS:T use a heavily modified version of InEn, especially Torment.

What is so modified about IWD. It looks very much like BG and BG2. I can see that PS differs somewhat (and I don't mean just the look and feel), but what's so different about IWD?

I should've written "use a modified version", Torment especially.
As you say, little was modified in the IWD engine, except some rules & spells that were implemented wrong in the original BG. Aside from that, there's little difference.

Black isle is part of interplay, they published it, bioware made it (programming, etc) or vice verca, Black Isle is interplay.