The man in question's name is Renato Constantino.
He was never the leader of the CPP, but was a member of an undercover cadre with the codename of "Kaka", who was charged with organizing street protests in Manila.
While he was in prison in 1988, a Christian police captain named Balligi Tira witnessed to him and over a period of months, he decided to become a Christian.
Tira's congregation, Greenhills Christian Fellowship apparently got involved with Warren's PEACE initiative a few years ago, and Constantino is now a volunteer and organizer for PEACE initiatives.
Constantino was not converted by reading The Purpose Driven Life - which was published in 2002, 14 years after he converted.
So when Warren writes, as he does above, that: "this communist leader who had read The Purpose Driven Life and accepted Christ and was now trying to serve the Lord" he is simply not telling the truth.
I'll point out that the paper in which this article was published, the July 23, 2006 edition of the Philippine Inquirer is an English language newspaper.
I found something similar here: Ex-communist finds purpose-driven cause. If this is the article Warren saw, the title might have thrown him off.
Because so many lives have been changed through Warren's ministry, I try to give him the benefit of the doubt.