John Adams too wrote a book that posited pagan Greco-Roman religion as “rational, intelligible, and eternal, for the real happiness of man in society, and throughout his duration.” If the orthodox carefully examined that book as they did Jefferson’s, it seems to me, Adams could have gotten in as much trouble as did Jefferson.
I'm not so sure, because Adams doesn't say that pagan Greco-Roman religion is "rational, intelligible, and eternal, for the real happiness of man in society, and throughout his duration"; he says that Zaleucus's preamble to his laws places religion, morals, and government on a philosophy which it serves as a basis that is "rational, intelligible, and eternal &c." But while the original context is pagan and Greco-Roman, it's unclear, in fact, that what Adams identifies as the content of Zaleucus's preamble would have been regarded by anyone as particularly pagan or Greco-Roman at all; the view argued for by Adams in the work from which the text comes, i.e., that government is subject to progressive improvement that successively uncovers the eternal principles of good government, is an extremely common one in the period. Read in that context it's fairly innocuous; one reads it naturally as simply saying that Zaleucus was one step closer to the ideal republic than his predecessors because he built his laws on eternally true principles, without, however, coming as close to that goal as his successors. (I think Rowe handles the passage better in a later post.)
Incidentally, Adams is simply adapting Cicero here. Tracing the influence of Cicero in this period is difficult, since something that sounds like it might have direct Ciceronian influence might actually just be second-hand. But Adams had a pretty hefty collection of Cicero in his library, and, equally importantly, Lord Kames actually gives us a text for Zaleucus's preamble, and Adams's summary fits it only very loosely (it fits Cicero's discussion very well). So either Adams had a text of Zaleucus other than that of Home's, or (much more probably) he misread Cicero's philosophical expansion of the preamble as Cicero's summary of it. A good example, one of many, of the importance of Cicero in early modern political and moral philosophy.
UPDATE: He has a very good post in response, and notes a letter from Adams to Jefferson in which Adams mentions Zaleucus again.