Cody Wilson, 31, pleaded guilty in August to injury to a child after initially facing sexual assault charges. In addition to probation, he must register as a sex offender, undergo counseling and perform 475 hours of community service.
He will not be allowed to own a firearm while on probation. The teenage girl and her family agreed to the lesser charge, prosecutors said.
The girl said she met Wilson on SugarDaddyMeet.com and eventually went with him to a hotel in Austin. There they had sex. She said she was paid $500.
Wilson was arrested in Taiwan last year after missing a flight back to the U.S. to face the charges. He founded Austin-based Defense Distributed, where he sold blueprints for untraceable 3D-printed guns.
The sales stirred the ire of gun-control advocates, who argued the weapons would pose security challenges during screenings at airports and other venues.
Wilson later defied a federal court order to stop posting the plans online. He resigned from the company after his arrest.
The Associated Press contributed to this report.