I'm not a 100% sure what drug rap exactly means, but if you're asking if he had to this ordered by the court, then pretty much yes.
He was originally sentenced to 5 years in prison, but was sent on probation.
He had to pay 250,000$ and part of his fine was that he had to support the Make A Difference Foundation. Hard to tell what the demands exactly were, but both the album Stairyway To Heaven - Highway To Hell and the Moscow Music Festival were essentially also projects he had offered in court to avoid going into prison.