Jason Halman has been held since the fatal knife attack on Nov. 21, 2011, when Greg Halman died after going to his brother's apartment after hearing loud music in the early morning hours.
Prosecutors in the case have joined the defense in asking for Jason Halman's acquittal on manslaughter charges, according to wire service reports out of Holland.
A final decision by the Rotterdam District Court is expected on Aug. 30.
The younger Halman's release was ordered on the advice of psychiatrists at the Pieter Baan assessment center, after determining he was having a psychotic attack at the time of the fight, according to Dutch News.
The news agency said Jason Halman has agreed to voluntarily come under probation officer supervision to ease his return to society and he could still be ordered to undergo psychiatric treatment.
The Algemeen Nederlands Persbureau (ANP) news service said Halman's mother told the court that both sons were victims in the case, and the family continued to support Jason even while grieving his brother's death.
Greg Halman was 24 at the time of his death. The outfielder had played parts of the 2010 and 2011 seasons with the Mariners, batting .207 with two home runs and nine RBIs in 44 games.
Jason Halman, two years younger than his brother, was an amateur baseball player in Holland. He visited Greg and stayed with him and his teammates several times during his last two seasons with the Mariners and the Triple-A Tacoma Rainiers.
The two were extremely close and were living in the same apartment complex after the Mariners outfielder had returned home for the offseason.