Assange was granted a conditional release on $316,000 bail Tuesday, but British prosecutors are apparently and appealed the decision to London's High Court.
Assange has already spent more than a week in prison following his surrender to British police over a Swedish sex-crimes warrant. He denies any wrongdoing but has refused to voluntarily surrender to Sweden's request to extradite him for questioning.
Special Report: WikiLeaks
Supporters of the 39-year-old Australian say the charges are trumped up and possibly politically motivated.
Assange's British lawyer, Mark Stephens, said Wednesday that "somebody has it in for Julian Assange and we only can conjecture why."
Speaking to media Thursday morning as he headed into court, Stephens said donors had contributed the necessary bail money, which the court wanted to see up front, in cash.
The New York Times reports, meanwhile, that the United States is against Assange. Prosecutors are searching for evidence of "collusion in his early contacts with an Army intelligence analyst suspected of leaking the information."
Lawyer Gemma Lindfield, acting for Sweden, told Tuesday's hearing at the City of Westminster Magistrates' Court that Assange faced serious allegations and may abscond if granted bail.
She said he is accused of rape, molestation and unlawful coercion by two women for separate incidents in August. Assange has yet to be charged.
Although the request to reverse the bail decision was widely reported Tuesday to have been at the request of Sweden, reports in the British media on Thursday said the Swedish prosecutors had no opinion on Assange's bail request.
Karin Rosander, director of communications for Sweden's prosecutor's office, told The Guardian: "The decision was made by the British prosecutor. I got it confirmed by the (Crown Prosecution Service) this morning that the decision to appeal the granting of bail was entirely a matter for the CPS. The Swedish prosecutors are not entitled to make decisions within Britain. It is entirely up to the British authorities to handle it."
Assange's lawyers say the allegations stem from a dispute over "consensual but unprotected sex" and argue that he has offered to make himself available for questioning via video link or in person in Britain.
Lindfield also rejected attempts to link Assange's case with the work of WikiLeaks - which last month deeply angered U.S. officials by beginning to publish its trove of 250,000 secret U.S. diplomatic cables.
"This is not a case about WikiLeaks, rather a case about alleged serious offenses against two women," Lindfield said.
District Judge Howard Riddle approved bail on Tuesday on condition Assange wear an electronic tag, stay at a specific address in southern England, report to police every evening and observe two four-hour curfews each day besides putting up the bond.
The address where Assange would live if released Thursday is reportedly the home of journalist and Frontline Club founding member Vaughan Smith.
Smith lives on a large estate called Ellingham Hall in Bungay, England.