After the Montreal Canadiens acquired Devan Dubnyk from the Nashville Predators in exchange for future considerations, speculation ramped up immediately because Dubnyk was available on waivers just yesterday. If the Habs wanted him, why not just claim him for free? Did Carey Price suffer a setback? Is he out for the season?
The reason he wasn't claimed off of waivers is because the Canadiens are penny pinching against the cap, and today the Predators offered to retain 50% of his remaining salary, 50% of his total already being retained by the Edmonton Oilers, which means that Montreal is on the hook for just 25% of his remaining salary this season.
Trading for Dubnyk also allows the Canadiens to retain Dubnyk when Price returns from injury, as they can send him to Hamilton without losing if he goes unclaimed on waivers.
Having a second NHL quality goaltender outside of Peter Budaj also allows them to be very careful with Price, who is their MVP this season, and possibly their most valuable player over the next few seasons. Rushing him back from injury is just a bad idea.
It's really not that complicated of a situation, and the rampant speculation doesn't make much sense.