Q:

When James and Jude use κύριος is their meaning limited to "master"?

In his book, The Jesus Dynasty, James Tabor asserts that James and Jude, which he takes to written by Jesus' brothers, use the term κύριος to mean something like "master".  It was a sign of honor for an older brother and mentor.  He contrasts that with Paul, who uses the word to mean "Lord" and (according to Trinitarian Christianity) equates Jesus to God.
Thayer's Greek Lexicon gives several* meanings to the word:

universally, of the possessor and disposer of a thing, the owner

a title of honor, expressive of respect and reverence, with which servants salute their master

this title is given to:
a. God, the ruler of the universe
b. the Messiah

Is there any evidence from the texts of these letters that Jude and James intended κύριος to not include the "title given to God"?

Footnote:

There is also a fourth meaning given but it seems to be disputed.  It also relates specifically to Paul, so it doesn't seem to apply to this question.

A:

The principal meaning of the Greek word κύριος is "master," and this meaning, I believe, is the one most frequently associated with the word by all NT authors alike. Certainly there are some instances where κύριος is being used as the equivalent to the Tetragrammaton יהוה, but these are the minority.
Paulos certainly does not always (nor even mostly) use κύριος as an equivalent to the Tetragrammaton יהוה.
For example, in Romans 6:11, it is written,

Likewise reckon ye also yourselves to be dead indeed unto sin, but alive unto God through Jesus Christ our Lord.
οὕτως καὶ ὑμεῖς λογίζεσθε ἑαυτοὺς νεκροὺς μὲν εἶναι τῇ ἁμαρτίᾳ ζῶντας δὲ τῷ θεῷ ἐν Χριστῷ Ἰησοῦ τῷ Κυρίῳ ἡμῶν

Here's what we need to understand. When κύριος is being used as the equivalent of the Tetragrammaton, it must be treated as a proper noun (a name). On the other hand, when it is being used in the sense of "master," it must be treated as a common noun.
In Romans 6:11, is it being used as a proper or common noun?
Since Paulos used a possessive pronoun (i.e., ἡμῶν, "our") with κυρίῳ, then it's undoubtedly a common noun, and thus, it means "master."
In any language, you simply never use a possessive pronoun in conjunction with a proper noun except for colloquial speech (which does not always follow the standard rules of grammar).
For example, one would not say, "Our Jon Ericson," but one could say, "Our friend." Likewise, one would never say, "Our YHVH," but one could say, "Our creator."
So, when we see κύριος written in conjunction with a possessive pronoun, then it should be understood as meaning "master," rather than being a reference to the Tetragrammaton.
The relevance is that Paulos quite often uses κύριος in conjunction with a possessive pronoun, so to say that Paulos uses the Greek word κύριος in order to equate Jesus as "God" is not entirely correct. He does this sometimes, but usually when he is quoting a passage from the Tanakh.
For the most part, he and other NT authors are using it in the sense of "master." The main reason is that the Greek word Χριστιανός (English: "Christian") means, "belonging to Christ," i.e. Christ's servant/ slave. Hence, Christ is literally our master, and we are his slaves/ servants.

James 5:10-11 is one example where it seems that James uses the Greek word κύριος in the sense of the Tetragrammaton rather than "master."

Take, my brethren, the prophets, who have spoken in the name of the Lord, for an example of suffering affliction, and of patience. Behold, we count them happy which endure . Ye have heard of the patience of Job, and have seen the end of the Lord; that the Lord is very pitiful, and of tender mercy.

Prophets speaking "in the name of the Lord" is a common expression in the Tanakh, translated from the Hebrew phrase בְּשֵׁם יְהוָה (beshem YHVH) (cp. Deut. 18:22).
Of course, "the end of the Lord" is referring to the ultimate reward that YHVH gave Job after he endured his trials.
As these are two examples where the Greek word κύριος is being used as an equivalent of the Tetragrammaton, rather than "master," need we find more in order to refute Tabor's hypothesis?

