Q: (1) What is the exact reason for celebrating the twenty-seventh of Cheshvan? Are the seven Mitzvot of Noach an integral part of the covenant between G-d and humanity which is symbolized by the rainbow? Or, alternatively, were the Mitzvot given at a later date, such that there is no reason to include them in a celebration of the day?
(2) Is there a "red line" that must not be crossed in celebrating in order to avoid the prohibition of creating a new religion? For example, is it permitted to give the day a name, such as "Noach Day," and to light a candle?
(Note: The twenty-seventh of Cheshvan this year was on Monday, November 12, 2012.)
A: (1) Noach received the Seven Mitzvot on the day that he left the ark, the twenty-seventh of Cheshvan. Therefore, in some ways this can be considered as the day when the Bnei Noach "received the Torah."
(2) The prohibition of creating a new religion mentioned by the Rambam is limited to an initiative by the Gentiles, as he writes: "The general rule is that we do not allow them [the Gentiles] to create a new religion and to make up new mitzvot for themselves" (Rambam, Laws of Kings, 10,9). This implies:
(a) There is no problem if the initiative is that of some rabbis.