Regarding copyright issues, Amy Welborn writes:
The requirements to cite, for example, from the New American Bible, the official USCCB English translation, are fairly strict. I don’t remember what they are, but all you really need to know is that most Catholic publishers don’t even bother to use the NAB. They tell their authors to use the RSV or NRSV, not just because of the quality of translation but also because of the degree of hassle and expense involved in getting permission from the respective copyright holders.
Which probably, in the end, and act of God and all for the good, considering how dreadful the NAB is.
Jeffrey’s posts and the comments on them concern primarily the liturgical texts published by the ICEL. That is, the English words used at Mass and so on. Even if you are quoting, say, the words of the Creed that we say at Mass in a book, you must get permission from ICEL. You don’t have to pay a fee at that point, but you do have to get permission and you must observe the exact line breaks that the ICEL translations use.