I don't know all of the intricacies of the salary cap, restrictions, free agency, exceptions, etc.. but I do know that I'm looking at the contracts on hoopshype.com, and Ariza is only signed for this year. Seeing as though the Knicks have no money to spare, can someone explain how the Knicks could resign Ariza?

On a side note.. why is John Amaechi on the Knicks payroll?

One of the main exceptions of the NBA's "soft" salary cap is that teams can always re-sign their own free agents regardless of the team's cap situation. In fact, teams can actually offer their own free agents more than other teams can (see Houston, Allan). This is why the Knicks' payroll is over $100 million -- even though the salary cap is only around $43 million. This also is one of the main reasons why there is not nearly as much free-agent player movement in the NBA as in MLB and the NFL. The NFL, on the other hand, has a "hard" cap, meaning teams are not allowed to ever go over the cap. This is why every offseason, NFL teams are forced to cut big-name players who make a lot of money. Teams have to get under the cap just to be able to sign their draft picks, never mind brining in veteran free agents to fill holes.