The judge said at the sentencing hearing that Moralez seemed "older than her chronological age."
The sentence drew protests for being too lenient and outrage over comments the judge made that appeared to pin some of the blame on Moralez.
State officials say Rambold must register as a sex offender and will remain on probation as prosecutors appeal the case to the Supreme Court in hopes of sending him back to prison for a longer term.
Rambold's attorney, Jay Lansing, declined to comment on the defendant's release.
In court documents and during the sentencing hearing, Lansing described his client as a one-time offender with no prior record who took responsibility for his actions when he admitted to a single count of rape under a 2010 deferred prosecution agreement that was made after Moralez killed herself.
Hanlon has said Rambold's actions were a "major factor" in her daughter's suicide. Moralez felt guilty for ruining Rambold's life, and was ostracized and ridiculed by her peers after details in the case became public, Hanlon said.
The agreement with prosecutors allowed Rambold to remain free for more than three years until he was kicked out of his sex offender treatment program for unauthorized visits with relatives' children and for not disclosing that he was in a sexual relationship with a Washington woman.
At the time, Rambold had been renting an apartment in Billings and working as a telephone trainer for a technology company, according to court documents.
When Rambold came back before the court in August, Baugh appeared to show sympathy for the defendant and agreed with Lansing's recommendation that Rambold receive a 15-year sentence will all but one month suspended.
The judge also made comments pinning some of the responsibility in the case on Moralez, whom he described as "older than her chronological age."
The comments drew a strong backlash from many women's groups, victims' rights advocates and others, who said the judge was blaming a victim who had not reached Montana's age of consent, which is 16.
Prosecutors said Baugh's lenient sentence was not allowed under a state law that requires Rambold to serve a mandatory minimum of two years in prison.
A formal complaint to have Baugh removed from the bench for alleged bias is pending before the state Judicial Standards Commission.