James is talking about the imperishable seed will always show itself, else it is dead.
James 2:20
You foolish man, do you want evidence that faith without deeds is useless?
Can we choose the fruit of the imperishable seed? No.
James 2:26
As the body without the spirit is dead, so faith without deeds is dead.
James 3:13
Who is wise and understanding among you? Let him show it by his good life, by deeds done in the humility that comes from wisdom.
James calls these unbelievers to repentance and faith.
James 4:8-10
Wash your hands, you sinners, and purify your hearts, you double-minded.
Grieve, mourn and wail. Change your laughter to mourning and your joy to gloom.
Humble yourselves before the Lord, and he will lift you up.
So this letter is written to those who claim to know Jesus, some of whom do and some clearly do not.
James 5:19-20
My brothers, if one of you should wander from the truth and someone should bring him back,
remember this: Whoever turns a sinner from the error of his way will save him from death and cover over a multitude of sins.
The warning is some are lost sinners, who are in spiritual death and end in judgement.