The verse in question is Exodus 23:13, which reads (in part), "Do not pronounce the name of another deity. You must not let it be heard through your mouth." (The Living Torah, translated by Rabbi Aryeh Kaplan, Maznaim Publishing Corporation)
On that verse, Rashi indicates that you shouldn't use an idol as a landmark ? as in, "wait for me besides such-and-such idol" ? or reference it similarly as a time landmark ? as in, "the day of such-and-such idol". He also gives an alternative interpretation that the verse is to teach that idolatry is as important as all of the other commandments combined. Interestingly, he doesn't clarify whether the verse means that it is prohibited to even speak the idol's name. (Rashi's Commentary on the Torah, translated by Rabbi Yisrael Isser Zvi Herczeg, Mesorah Publications, Ltd.)
Nachmanides takes a somewhat different approach. He gets very specific and says that one shouldn't even mention the name of their gods such as - and he goes on to mention four of them by name. Then he says that one should refer to them in a manner of condemnation, such as "the abhorrent thing of Moab", and "the abomination of the children of Ammon". He then adds that it's possible that the meaning of "make no mention" means not to mention the name of other godsto their worshippers (my italics added). (Ramban Commentary on the Torah, translated by Rabbi Dr. Charles B. Chavel, Shilo Publishing House)
Sforno takes the position that one shouldn't even mention the idol's name. (Sforno Commentary on the Torah, Translated by Rabbi Raphael Pelcovitz, Mesorah Publications, Ltd.)
Maimonides offers us an interesting paradox. In his Laws of Idol Worship And Its Regulations (see http://www.panix.com/~jjbaker/MadaAkum.html; thanks to Rabbi Moshe Ben-Chaim for this URL), the last sentence of Chapter 5, Section 10 reads, "Even to make mention of the name of an idol not by way of an oath is forbidden, for it is written, `...and make no mention of the name of other gods'." However, note that in Chapter 5, Section 11, he states, "Any idol mentioned in Scripture, such as Pe'or, Ba'al, Nebo, Gad, et cetera, may be mentioned by name." Rabbi Moshe Ben-Chaim also pointed out to me that the Shulchan Aruch, Yoreh Dayah 147:4 and Maimonides' Laws of Star Worship 5:10 appear to make it prohibited to mention the idol's name for any purpose.
Just to make it even more interesting, Jack Saunders noted that, in the Rambam'sMishneh Torah, Hilchot Mecachim, Chapter 11:4, he writes Jesus of Nazareth in Hebrew.
So let's summarize some of the questions here.
(1) How do we reconcile what appear to be conflicting statements by the Rambam?
(2) Can we, or can we not, say the name of Jesus?
(3) Does any of this devolve upon Noahides anyway, at least halachically?
(4) What about saying names today that once were idols, but aren't considered so any more, such as January or Apollo?
The statements of the Rambam combined with the fact that he wrote the name Jesus suggest that one of two things must be true. Either the Rambam was only talking about oral statements (so that writing the name of Jesus wouldn't be a violation), or he concluded that "Jesus" is not an idol.
According to Rabbi Chait, door #2 is the correct one. Rabbi Chait indicated that you can say the name of Jesus because he's a human being, not a god. He pointed out that the difference between Jesus and (prohibited) idolatrous names is that a stone is a true idol. However, Jesus' name was Jesus at first. The people then later decided to make him a god, and called him by his name. Stone idols, by contrast, were idolatrous in their inceptional form, so their names were always related to their definition as an idol. But Jesus was a man first ? and the name was used that way ? and only later did some people make that name into a god.
This clears up our question around the Rambam. He can write the name Jesus because of the reason given above. At the same time, he can hold that idol names shouldn't be used. That also tells us that we can say or write the name Jesus. So that covers questions (1) above, and it also covers question (2), regardless of the answer to question (3).
Regarding question (3), Rabbi Chait said that Exodus 23:13 does not apply to Noahides, but swearing in the name of a god does apply as this is recognition of the god. So that takes care of question (3).
But what about names like January or Apollo? We already know that we don't have a halachic prohibition here because of the answer to (3) immediately above. Further, Rabbi Chait pointed out that only names that signify exclusively a currently worshipped god are prohibited (which also ties back to why "Jesus" is permitted, since it is not exclusive but is also used as a person's name). Now when I say January, I am not referring to an idol. In fact, until this topic came up in this news group, I had no idea that January had idolatrous roots. Ditto for many other similar names. When I say January, I'm referring to the month. When I say Apollo 13, I'm referring to the moon shot, or the movie of the same name. When I say Taurus, I'm referring to a Ford automobile. From a practical standpoint, it's impossible for me to know the origin of every word in our language, and I have to be able to operate in society. Thus, even if Noahides were halachically prohibited in this regard ? which they're not ? it is ok for me to use those names since I'm using them to refer to something in the practical world, not an idol.
It's important to note that there is nothing magically taboo about an idol name. It would be easy to go down the road of thinking that something cosmically bad happens when an idol name is used. Yet idols, by definition, are nothing. Thus, saying their name can't be doing anything cosmically in any way, except that it potentially gives credence to the idea that they mean something other than nothing. Thus, we can see a reason (not necessarily all reasons) why the Torah would tell the Jewish people not to even utter them. The Torah doesn't want the Jewish people to give any credence to anything that is not real. And idols are certainly not real.
Thanks to Rabbi Chait, Rabbi Moshe Ben-Chaim, and all who contributed to this.