In an interview with Aljazeera, Anwar stressed the necessity for an independent judiciary in his country.
Sitting in a wheelchair and wearing a neck brace, the former deputy premier and finance minister said a "political conspiracy" had been hatched against him "at the highest level".
While not denying his release might have come because the government realised he no longer poses any political threat, Anwar affirmed that no political deal had been reached for his release.
In an earlier interview with AP on Saturday, Anwar said "it's an indescribable feeling to be among family and friends". He was looking far more relaxed than during a tense appearance on Thursday, when Malaysia's highest court reversed his conviction.
Anwar stressed he would never have been let out of prison if his former boss, retired prime minister Dr Mahathir Mohamad, was still in power.
And he praised Mahathir's successor, Abdullah Ahmad Badawi, for allowing such a ruling.
"It would have been impossible if Dr Mahathir had been reigning, because he would have ensured the judgment was scripted," Anwar said.
He said his priority now was to push through reforms - a freer media, fair elections and independent judiciary - and that he would work closely with an opposition alliance that includes a party headed by his wife, Wan Azizah Ismail.
"What needs to be done is ensure the reform agenda, and that the injustices perpetrated against others must be stopped," Anwar said. "That, unfortunately, is not happening as much."
Anwar maintained that a "silent majority" supports him.
"I have been maintaining that the institutions of civil society must be allowed to function," Anwar said. "It would give more latitude for people to express themselves."
Anwar's supporters have long
maintained his innocence
The ruling that freed him came exactly six years after Mahathir - a combative figure who transformed Malaysia into one of Asia's wealthiest countries but was often accused of dismissing democratic procedures - fired Anwar as his heir-apparent in a power struggle.
Anwar then led tens of thousands in anti-Mahathir demonstrations and was arrested on 18 September 1998. He was beaten in custody and he was convicted on sodomy and corruption charges.
Anwar, sentenced to prison terms totalling 15 years, repeatedly accused Mahathir of orchestrating a judicial conspiracy to destroy him, a charge which Mahathir consistently denied.
Rights groups criticised the trials as unfair. Anwar's appeals had failed until Thursday.
Anwar had at least five years more to serve in prison. He had already served his sentence for the conspiracy conviction.
Anwar said it was "premature" to discuss whether he would ever return to the ruling United Malays National Organisation (UMNO), now headed by Prime Minister Abdullah.
"I don't preclude any discussions with UMNO - not with the view of rejoining it, but to agree on some common agenda of reform"
"I don't preclude any discussions with UMNO - not with the view of rejoining it, but to agree on some common agenda of reform," he said.
He acknowledged that he and Abdullah had once been rivals, but said their relationship was "civil".
As a convicted felon, Anwar remains barred from seeking office for another five years. But a new Federal Court panel is scheduled for Monday to consider whether to review an earlier decision to uphold the corruption conviction. If successful, Anwar could return to politics immediately.
The politician called for the release of detainees held under the Internal Security Act (ISA), a relic of British colonial rule that allows for indefinite detention without trial and a law that Anwar once defended when he was the nation's second most powerful man.
Detention without trial
The law is currently being employed to hold about 70 suspected members of the Jamaah Islamiyah group, but has been used by leaders to jail political opponents in the past.
Human Rights Watch has said the ruling of Anwar's release highlights the continuing detention without charge or trial of nearly 100 security detainees in Malaysia.
In a statement, the organisation renewed its call on the government to begin processing the cases of ISA detainees, some of whom have been held without trial for more than three years.
"It took six years for Anwar to get a fair hearing," said Sam Zarifi, deputy director of the Asia division of Human Rights Watch.
"The hundred or so other detainees still held under the Internal Security Act shouldn't have to wait that long. The Malaysian government needs to either charge them with a crime or release them."