- World of Warcraft game director Tom Chilton.

Blizzard drew a bit of ire from World of Warcraft fans earlier this year when it effectively shut down (via threat of legal action) a popular private server, Nostalrius, running an unauthorized legacy version of the game for an estimated 150,000 players.

More intriguingly, it drummed up fresh conversation about an important topic: How do you best preserve games, especially older versions of a persistent, regularly-updated game like World of Warcraft? What if you don't actually have access to your original game? 

Blizzard representatives have made it clear they threatened legal action against Nostalrius in order to protect the company's IP rights, not stifle fan efforts to preserve older versions of their game.

Now, in a recent interview with Kotaku, World of Warcraft game director Tom Chilton and senior art director Chris Robinson have shed light on the technical challenges Blizzard faces if it tried to replicate World of Warcraft the way it was at launch, back in 2004.

"In the past, there was no archiving of older data," said Chilton. "So while we have the capability of doing that now, and in more recent years when we make changes we can ‘version’ the data, we didn’t have that back in 2004. And so as data changed, we effectively lost that stuff to history. And so we would have to go back and try to reverse-engineer it ourselves."

That, says Chilton, is exactly what the folks behind Nostalrius did -- they "spent countless hours researching" old versions of World of Warcraft and did their best to reverse-engineer the entire game.

"They’re just kinda guessing and approximating on a lot of stuff. Which is cool, and they did an amazing job of making it feel like a very authentic experience," said Chilton. "But ultimately the way they implement their data is in no way similar to the way we do it. So it’s not like we can even take that data and put it in the game, because they actually aren’t even really compatible - they have a completely different approach to creating content."

He goes on to note that Blizzard sees challenges in even just hiring the Nostalrius team to run a legacy server for Blizzard, due to the challenge of integrating it with Blizzard's existing Battle.net infrastructure.

There's also a fair bit of conversation about Blizzard's current process for developing World of Warcraft expansions in the full Kotaku interview, which is well worth reading if you're at all interested in how the creator of one of the biggest MMORPGs in the business keeps it afloat.