http://www.thescore.com/news/788316
The reasons for Ridnour getting dealt so frequently are a matter of salary cap minutiae, but here's a quick explanation: Ridnour's $2.75-million contract is non-guaranteed until July 11, which serves to make him an attractive trade chip, enough so that it's quite likely he gets traded again.
A non-guaranteed deal can essentially serve as a salary cap exception. Because salaries have to closely match in trades - the exact proximity of incoming and outgoing salary changes depending on the cap situation of the teams involved - a non-guaranteed deal allows teams to artificially inflate the amount of outbound salary in a trade, allowing them to take on more incoming salary.
To illustrate for the Raptors: Say they wanted to sign-and-trade forLaMarcus Aldridge, allowing Aldridge to get a slightly larger four-year max from the Portland Trail Blazers instead of the four-year max Toronto can offer. The Raptors could clear the requisite cap space and take Aldridge into their cap room, but they'd have to renounce the rights to several of their free agents to do so. If they can send Portland enough salary, they can take Aldridge on and keep the rights to at least some of their free agents, while also helping Portland recoup something in the deal.
Having Ridnour's $2.75-million deal on hand gives the Raptors a means of sending out more salary, and Portland can turn around and waive Ridnour at no cost to themselves.
These same machinations would be true for any deal Toronto - or Ridnour's next team - wanted to make. When free agency begins on Wednesday, teams can't make moves until July 9, so Ridnour's window of trade utility exists for July 9 and 10 only. It remains possible the Raptors keep Ridnour - head coach Dwane Casey and new assistant Rex Kalamian are said to be fans - but he'll almost certainly be waived ahead of July 11 if he's not included in a trade of some sort.