The release as Jonas understands it in Chapter 4 is a happy occasion where a person's life is celebrated and then they are "released" to a mysterious place. Jonas feels pretty good about the idea of release, and finds comfort in the House of the Old. However, he is still a bit perplexed and curious as to the details and specifics of what "release" actually entails. No one can answer his questions, but they emphasize that the important thing is that everyone is very happy about the releasing ceremony, and that it is a happy occasion.
Later on when Jonas learns what is truly meant by release, the book takes on a very dark tone. He learns from the Giver, who makes him watch the video of his very own father "releasing" a newborn baby which was the smaller of two twins. Rather than being a pleasant farewell ceremony where the infant is whisked away to new parents in the elsewhere land, his father takes a needle and euthanizes him. In a graphic description of the baby kicking and jerking before dying, readers see that the ideal, utopian society is also a very cruel, unfeeling place to live one's life. The father didn't flinch as he did this terrible act. I still shudder when I read this part of the book with my classes.
This is an opinion question, which only you can answer, based on your reading of the chapter. There are some things which you will definitely have to take into consideration, however.
Most of the information presented in this chapter about Release is given by Larissa, a resident of the House of the Old. Larissa talks about a Ceremony of Release she witnessed just that day, that of Roberto, who had lived a very full life. Larissa says that they told his whole life story before they released him, and that this telling was followed by a toast and a cheer, the chanting of an anthem, and "a lovely good-bye speech" given by Roberto himself. Larissa is almost ecstatic at the memory of the celebration; she says, "It was wonderful", and that the look on Roberto's face as he bowed and walked through "the special door in the Releasing Room", never to be seen again, was "pure happiness". Larissa's account of the Ceremony of Release is completely positive, and she even wonders why they don't let children witness these celebrations too.
There is only one indication in this chapter that Release may not be all that the people think it is. Jonas asks, "what happens when they make the actual release? Where exactly did Roberto go?" Larissa does not know the answer, and, perhaps portentously, does not seem to care. In forming your own opinion on the subject of Release after reading this chapter, you will have to decide whether Larissa's evaluation is accurate, and whether the casual question posed by Jonas is simple curiosity, or something more ominous (Chapter 5).