If you look at a few places James uses κύριος or related, they are all about God, Jesus or Sabaoth. Whomever you take Sabaoth to be (he's the commander of Yahweh's army who discloses the weakness of Jericho such that the walls then collapsed, or he's Yahweh, or he's Jesus, or he's Sabaoth, you tell me...).
Also, I have not read the book you mention. I don't know if I have time with all thte James commentaries I have piled up. But I will say this clearly:
James called Jesus the Christ in the first verse of James, 1:1:
1:1) James of God and of Lord Jesus Christ, slave to the 12 tribes of the diaspora, greetings:
That word Christ is in the Greek MS as Xrictou. So James is clear on what he thinks of Jesus. He does not think of him as a good carpenter, a big brother, or a mere cool dude. James is strongly a Jew and calls Jesus the Christ. In 5:6 he refers to him as "the righteous one" as in the same word that Abraham was reckoned "righteous and a friend of God." To James, dikaion, or righteous, meant beloved of God.
So I dunno if we have to dig into a theory around κύριος, do we? If we do...
James 1:7 uses κύριοu to mean "of the Lord" referring back to 1:5's antecedent, theou, of God.
James 1:12 uses κύριος to mean God again.
James 2:1 uses κύριοu to refer to Jesus. Read this:
2:1) My brothers, do not be having partialities in the faith of the Lord (κύριοu) of us, Jesus Christ, Anointed of the Glory.
Now if you read 2:2-2:4 at least you will see that in 2:1, he is saying, "When you are in church to worship the Lord Jesus Christ, if a man shows up with a gold ring and splendid clothes, and you seat him in a quality seat, but a poor man shows up in poor clothes, and you place him under the underfoot of you, or tell him to go stand over there, then you are having unjust judgings of you.
2:1 is about where people would sit in church worshipping of the κύριοy Jesus Christ, the Anointed of the Glory.
I would call that bigger than a guidance counsellor.
4:10 uses κύριοu and is part of the context 4:6-10 which is part of the overall 4:1-12 larger context. 4:13 is a bit of a turn in the road, but not a non sequitor. It's hard to know where to draw the boundaries around context in James, because it flows like an epic poem.
But however you slice it, you cannot read 4:10 without considering 4:8 and so once again, James means God when he writes κύριοu.
4:15 is again clearly referring to God in my opinion, what with the context of the preceding verse, 4:14. In 4:13-17 James is clearly talking about God again, and so 4:15 κύριος means God.
BTW, 4:15 is always misinterpreted. James means this:
4:13) Addressing now the ones saying, "today or tomorrow we shall be going in to the city and we shall be there one year and we shall go in and out and we shall profit"
4:14) who of you are not aware of tomorrow? for the aliveness of you consists of exhaling, which toward a few appears on-thereafter [(that is, tomorrow)], and then disappears.
4:15) Instead of that, you say, "κύριος should be willing and we shall be living and we shall be doing this or that." [Notice the disregard with which James describes that planned activity, "this or that." He does not usually write like this and it makes a point.]
4:16) Now (when you say 4:15) you are boasting in the exaggerations you make. Every such boasting is wicked.
4:17) Thus to one who has perceived the quality thing to do, and is not doing it, that is sin.
In other words, the thesis of 4:13-17 is that when you know what would be good to do in the eyes of the Lord God, shut up and do it. Specifically, do not say "κύριος willing, we shall live, and ..." If you know what the quality thing to do is, and you know you might die at any moment, and you don't do that quality thing, you are sinning.
Of course, this is obviously true. Not only would a quality thing to do potentially incur profit or going in and out of a city, a quality thing to do would please the Lord God, in James' view.
5:4 Is κύριοu Sabaoth. Look up Sabaoth. Make up your own mind.
5:7-8 are about the return of the κύριοu, the return of Jesus. He is the "righteous one" mentioned in 5:6, but 5:7-8 stand on their own, anyway.
Another person would dispute that the Righteous One of 5:6 is Jesus, but James word and analogy to Elijah make it clear he does mean Jesus in 5:6. Even if you take κύριοu in 5:7-8 to refer to Sabaoth, and believe Sabaoth is not a Christophany, Sabaoth is still a big deal. But in my opinion, 5:6 is clearly about Jesus, so κύριοu in 5:7-8 are about Jesus.
5:10 uses κύριοu and refers to the "name of Lord" spoken by "the prophets," I take this to mean κύριοu as of-Yahweh in this case.
5:11 uses κύριοu and κύριος and clearly refers to the God of Job, Yahweh.
5:14-15 is beyond textual analysis and gets into belief. I submit this is clearly a reference (κύριοu) to either Jesus or Yahweh. Given the action of removing sins from the dying brethren, this is God, either Yahweh or Jesus, the judge of sins who is being called on as κύριος in these verses. The anointing with olive oil is first described in Exodus.
I may have missed a κύριος, I sincerely hope not. I used my eyes and my paper copy of James to compile the above.
Here is the score:
κύριος Means Yahweh God: 6
κύριος Means Sabaoth: 1 or 3 (Sabaoth + Jesus == 4)
κύριος Means Jesus Christ: 1 or 3
κύριος Means God or Jesus who removes sins from dying brothers: 1
God or Jesus or Sabaoth Total: 11
On the other team:
κύριος means one who is anointed: 0
κύριος means mentor: 0
κύριος means respect for a mortal human, not the Christ: 0
κύριος refers to care bear: 0
I hope I didn't miss any κύριος, but w.r.t. James, I would say, no, the book you mention must be mistaken or otherwise corrupted by the adversary.
I don't yet know as much about Jude, can't help you there, yet.
About James, the book: It is short. At 108 verses, I can say I have read it in Greek more times than twice its verses. I would suggest if you want to get insight to this address (i.e., oration or sermon) of James' to his Hellenized Jewish Christian church, you should read it, a lot, in Greek. When you have read it 200 times, you may not have learned Greek, but you will certainly have learned James. And you will know that James very much believes that Jesus is the Son of God who is returning in the final days.
EDIT: I unfortunately spent some minutes reading excerpts from Tabor's book. I see that Tabor claims that "Christ" does not mean the Messiah who the Jews anticipated was to come, redeem humanity, and return in the Last Days. However I hope you will read James and see that this is absolutely, without any doubt, not an honest representation of what James believed.
Tabor is surely correct that Jesus had half-brothers, they are named. Otherwise, I saw lots of things that were clearly incorrect. There were too many to enumerate and address; there were innumerable incorrect statements about James in the excerpt of Tabor I reviewed. There were also some correct statements, but overall I wouldn't consider that a source that needs to go into my research.
Also, Tabor states that xrictoc means "anointed one." I am not sure it meant that to James. In James 5:14, when talking about actual anointing, the Greek word James chose was rather different from words related to either Messiah or Christ. If Tabor's suggestion that James mean something less than "Lord Jesus Christ" as we understand it today, and really meant, "Mentor Jesus Anointed-one," why did he change root words when what he actually meant "anoint?" Don't discredit James: he only uses the root words he means; he is incisive. I do not agree that James thought the word Christ or the phrase "Kuriou Jesuou Christou" to mean much less than Christians today would think it to mean. It's just not right.