Release of Terrorists in Exchange for Jewish Bodies

What is the justification for releasing terrorists in exchange for the bodies of Jews?

Shalom and blessings 

Excerpt from the article by our teacher, the Gaon, Rabbi Avraham Fried, shlita, on the matter: 

Release of Captives vs. Release of Terrorists:
A.
"From the firstborn of Pharaoh sitting on his throne to the firstborn of the captive who is in the dungeon" (Exodus 22:19).
It is explained in Targum Yonatan that Pharaoh held the sons of the kings of the subjugated nations [heirs to the throne]
as collateral and guarantee [see Kings I 20:13], and they too died because they rejoiced
in the subjugation of Israel, and similarly in the Mekhilta (Tractate de-Pesach, ch. 13) that the captives died because they rejoiced
in Pharaoh's decrees against Israel.
B.
It is stated in the Gemara (Gittin 45a) that captives are not redeemed for more than their value for the sake of the world's order. And in the Gemara there
are two reasons why they are not redeemed: either so that the community does not become impoverished, or so that it does not lead them
to capture more people and thereby earn money.
The difference between the reasons is in a case where there is no issue of money: according to the first reason, there is a need to care for the redemption
of captives, but according to the second reason, there is a discussion not to redeem.
Rambam (Laws of Gifts to the Poor, ch. 8, hal. 12) ruled the second reason, and so it is in Yoreh De'ah (ch. 252, sec. 5)
[see Ketubot 52 and Ran on the Rif (Gittin 22 according to the Rif's pages)].
C.
In Tosafot (Gittin 58) it is explained that in a place of danger to life, they redeem even more than their value. According to Tosafot, there is
a discussion in our case for permission, but Ramban (Gittin 55) wrote to disagree with Tosafot, as every captive
is in danger of death, and yet the sages forbade redeeming him for more than his value.
And in this matter, the later authorities differ, in the responsa of Maharam of Lublin (ch. 15) ruled that they do not redeem even in a place
of danger, and so it is in the responsa of Knesset Yehezkel (ch. 38), but in Beit Hillel (Yoreh De'ah 252) it is written that in a place of danger
they do redeem. And these matters are brought there in Pitchei Teshuva (sec. 4), and it is ruled that in a place of danger they do redeem.
D.
It is explained that captives are not redeemed for more than their value so that they do not capture more, and according to this, they do not redeem a captive
by releasing terrorists, as this will lead to capturing more people. However, there is a discussion that people
who fought may be redeemed, so they fight without fear, knowing that everything will be done to release them if
they are captured. However, if there is a danger to the captives, it is permitted even to redeem civilians who were captured. But if it is known for certain
that the released terrorists will kill more, this needs to be discussed.
E.
Entering danger to save one's friend, and putting others in danger to save one's friend:
It is written in Meshech Chochma on the verse "Go, return to Egypt, for all the men who sought your life are dead"
(Exodus 4:19), which proves that if those who sought his life were alive [i.e., if Dathan and Abiram were alive],
he would not need to go to bring the children of Israel out of Egypt, even though all Israel needs him, he should not
put himself in danger [and therefore only because Dathan and Abiram died, he was commanded to return to Egypt to save
the people of Israel]
And this is elaborated in Or Sameach (ch. 7, laws of the murderer) that one should not enter a doubtful danger to save his friend
from certain danger, and he brought from the Jerusalem Talmud (Ketubot, ch. 8) that one enters doubtful danger to save
his friend [even an individual, not a community], but he rejected that there is no proof from the Jerusalem Talmud, and he brought from the authorities (Choshen
Mishpat, ch. 426) on this matter.
And the opinion of Meshech Chochma above is that one should not enter doubtful danger to save his friend, and not even a community, and so is
the opinion of Netziv (in Haamek She'ela, ch. Re'eh), and see Pitchei Teshuva (Yoreh De'ah, ch. 157, sec. 9) that one who does so is a foolish pious, and so ruled Mishnah Berurah (ch. 329, sec. 19) regarding an individual that one should not enter doubtful danger if it is a true doubtful danger [and see Chazon Ish, Yoreh De'ah, ch. 69].
And those who disagree with Or Sameach above and believe that one should enter doubtful danger to save his friend [and all the more so
a community], need to explain how they interpret the above verse, and there is a lengthy discussion on this, and this is not the place for it.
F. 
It is explained that according to the law, one should not enter doubtful danger to save his friend, but only if it is a true doubtful
danger, but if it is a distant danger, one should enter this danger to save his friend. However,
to save people if others are put at risk because of this, there is no permission for this, especially if it is a reasonable risk.
And it is explained that one should not enter doubtful danger to save his friend, but in war, there is permission for this [as explained
in Minchat Chinuch, commandment 453].