This is a gigantic question ... is anybody free? What does that mean? How would we know?
If you take the viewpoint of the determinists, authors such as Theodore Dreiser, none of us are free; we are all products of the many forces that shape our lives as well as the interior drives (Freud) that drive us to do things that the rational part of ourselves might never agreee to. The classic summation of this "problem" is in St. Paul where, and I'll paraphrase, he says: the good things I would like to do, these I do not do; the evils that I seek to avoid, these I do. If you look into the works of modern behaviorists like B. F. Skinner, you'll get more of the same. For Skinner, we are molded by "positive reenforcement": put simply, perhaps too simply, we repeat behaviors that give us the positive feedback that we want, and these behaviors can be manipulated to help us make the "desired" decisions.
That said, was Squealer free? I doubt it. Squealer did what he had to to please the other pigs. He told whatever lies he needed to, grew fatter and fatter, and got what he wanted through his machinations. While he was manipulating, he was manipulated. Hardly free ....
Squealer is part of the authoritarian government structure; he acts as the propaganda mouthpiece for Napoleon. He is an insider, as free as Napoleon and his other henchmen.
"By the story's end, he is so fat that his eyes are mere slits. Always on the lookout for a new slogan, he teaches the sheep a new song to explain why the pigs are suddenly walking on their hind legs."
Squealer is fiercely loyal to his leader, he is said to be able to convince the other animals that everything Napoleon decrees is somehow good for them, even when it is cruel, like the reduction in their food rations for their longer work hours. Squealer is excellent at confusing the other animals into thinking that they are too stupid to understand the complexity of running the farm, therefore, only Napoleon is smart enough to make all the decisions. And, they must never question Napoleon.
"Like any good propaganda boss, he is able to not only explain the present, he is also an expert at rewriting the past. He makes the animals believe, for example, that Snowball never had received the order of "Animal Hero, First Class." But, of course, he had."
Squealer is a part of is the part of coterie that collude to serve their personal goals at the cost of other animals. He is definitely subservient to Napoleon, but it is evident that he enjoys more powers and privileges for the support he provides to Napoleon. As it is all the pigs in the animal farm are more privileged than other animals, and squealer is more privileged even among pigs.