Many relatives of the 270 people killed in the Pan Am airline bombing over the Scottish town of Lockerbie are still outraged over al-Megrahi's release. The vast majority of the passengers were Americans.
Scotland took the decision to release the bomber on compassionate grounds on August 20 last year, saying he was seriously ill with prostate cancer and had only a couple of months to live.
Al Jazeera's Alan Fisher, reporting from Edinburgh, the Scottish capital, said: "Many people are surprised that he [al-Megrahi] is still alive one year on. There's no doubt that the release of the Lockerbie bomber ... is still a big political argument."
He said the Americans are calling the release not "compassionate ... but convenient release [as] so many people benefited from the decision to free al-Megrahi".
"There're some who say that the whole Scottish legal system benefited because there were questions over the conviction, and if al-Megrahi had gone to a second appeal then that conviction would have been challenged perhaps overturned and the question would have been left: Who is actually behind the Lockerbie bombing."
"There are people in Scotland who request compassionate release and don't get it," Susan Cohen, whose 20-year-old daughter, Theodora, died in the bombing, said.
"There are people who die in Scottish prison," the 72-year-old US resident told the AP news agency adding "[al-Megrahi] may outlive me".
Al-Megrahi was released after serving just eight years of a minimum 20-year sentence.
Alex Salmond, Scotland's first minister, said al-Megrahi's release "had been done following the precepts of Scottish jurisdiction and Scots law".
"Some people say that the Scottish system has too much compassion," he told the AP news agency.
"But at the end of the day, I think I'd rather be first minister of a society with too much compassion than be first minister of a country with too little compassion."
However, some groups have speculated that energy company BP pressured the government to release al-Megrahi.
US senators allege the energy firm played a part in securing the bomber's release as part of its efforts to seal a lucrative exploration deal with Tripoli.
The US senate's foreign relations committee wants to hold a hearing into the affair in the coming weeks.
Officials in Britain deny BP was involved in the affair and the Scottish government has declined to send ministers to Washington to appear before the hearing.