Here is the wiki definition of spam.
Forum spam consists of posts on Internet forums that contains related or unrelated advertisements, links to malicious websites, trolling and abusive or otherwise unwanted information. Forum spam is usually posted onto message boards by automated spambots
or manually with unscrupulous intentions with one idea in mind: to get
the spam in front of readers who would not otherwise have anything to do
with it intentionally.
As long as he stays within those boundaries he is welcome to add a few links here and there as long as he does not abuse or go to extreme with his links... I hope you can understand my point on this.