“There's really no justification to make such a website.”

That seems like a very strange conclusion. How did you arrive at that? Wouldn’t it be good to know from yet another source that radiation levels currently really are nothing to worry about?

Their text: "This ongoing crisis has highlighted the need for trusted sources. With conflicting reports of radiation levels in affected areas, we wanted to build a way to report and see data in an unbiased format.

This site is not meant as a replacement for government nor official nuclear agencies. Our hope is that data sets from various sources can provide additional context to the official word in these rapidly changing events. ..."

They're using loaded language. They don't say that the official reading are not credible, but let's take a few measurements to make sure.

Background radiation levels vary quite a bit due to surrounding geographical features. A reading from a government station is made under a controlled environment, so a prolonged and large increase in their readings is a good indicator of possible contributions from artificial sources. Getting people to run around with consumer radiation meters isn't going to produce credible data, especially when people are more likely to submit a sample if they "find" an unusual reading.

Also, they're calling for contributions from people in Japan. Yet they do so not in their native language. It seems to me that their intent is that they want radiation readings primarily from English readers i.e. not Japanese.

So you have no problem with the concept, just this specific implementation? There are more understandable ways of saying that.