The letter has been posted on FailedMessiah.com (the letter is in Hebrew).
Here is my translation of it (it's almost a transliteration, actually, so it's quite precise):
Sunday, Week of Kedoshim, 13 Nissan 5770 [April 17, 2011]
I hereby announce to the public, regarding the righteous man Rabbi Shlomo Aaron Kellner, that what he did in respect to reporting to the authorities was done only after asking a Halachic question [from a qualified Rabbi], and that he did it in accordance with the views of our holy Torah (as clearly stated in responsa from prominent poskim – Halachic authorities). He has listened to the views of the Torah as is proper and lawful, and it is forbidden to cause him distress or to humiliate him, and certainly to inform about him [to the government]. On the contrary: it is proper to use all avenues to help him and to save him [from prosecution]. (emphasis added)
And he who transgresses on this will suffer Divine retribution.
The writer and signer for truth and justice:
Chaim Avraham Duber Flohr
We, too, join in emphasizing the words of the above great Rabbi, and it is a great mitzvah (Torah commandment) to save the victim from his oppressors!
And on this we come to sign on the above date:
Elimelech Yechezkel Shraga Gold
(I have posted the above translation as a comment on the page where the letter is posted.)
This is great news for our community. It means that more Rabbis have the courage to come out publicly in support of the Torah's view regarding child molestation, namely that it must be reported to the authorities. Other rabbis have already written clear responsa saying as much, but few have given public support for specific cases of prosecuting a molester.
May Hashem bless these Rabbis. Certainly their reward will be tremendous, as they are upholding the righteous ways of the Torah in spite of the many who will hate them for it.