Hasbro never gave them permission- I couldn't find that they claimed to have it, only that they claimed Hasbro technically couldn't stop them from doing this. Game Zone hasn't been very clear all along.
From what I've pieced together, here's what happened. Hasbro stopped renewing the trademark on Heroquest (which makes sense for a product they are no longer producing). That means that the name can be trademarked by other people (in the US Moon Design jumped on it, and in Spain Gamezone grabbed it).
Now owning a trademark on Heroquest does not give you any rights to anything that was previously associated with the trademark. So, while they had the rights to use the name 'Heroquest' they were not within their rights to imply that this is connected to the old Milton Bradley game.
Hasbro could have brought them to court over that, and raked them over the coals (Hasbro has won cases in the past where game elements were re-worded- and in this case Gamezone was advertising that they would be plagierizing the old rules set). The Moon Design people were worried that they would be pulled into the case if they did nothing to stop this, so they sent a cease and desist to Kickstarter (they don't have any connection to Spain, so don't have to worry about that).
Kickstarter isn't invested in Heroquest like Game Zone is, and there was simply on reason for them to go to court over it. Moon Design's complaint was reasonable, so they took it down.
Yes, there are a lot of crazy things that need to be worked out in court. Is Kickstarter a method of distribution? Are they investors or customers? If they're investors, then this isn't a problem, but they don't behave like investors in a lot of ways (Kickstarters do not receive financial returns on their investments, for example).
The thing is, you don't want your Kickstarter project to be the one that has to suffer through that court case. And we probably don't want Heroquest to be the thing that decides it all.
I feel that Gamezone have been working in this gray area- where what they're doing should technically be legal even though it looks like it totally isn't. As a small company, that isn't a good place to stand (especially when you are so publicly showing how much value the property has).