James, who came through the youth ranks at Sheffield United, has made 12 appearances for Vale since moving to Burslem in July 2011.
However, his last game for Vale was at the beginning of December and the 20-year-old has been allowed to leave to gain some first-team experience.
"Kingsley is a young player who has demonstrated his potential this season," said Vale boss Micky Adams.
"This move will enable him to get some valuable appearances under his belt and we wish him well.
James is expected to go straight into the Hereford squad for their Blue Square Premier clash against Mansfield on Tuesday night.
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