I would like a link explaining this. I seem to remember that players immediately become free agents once the season is over
Some items from the Larry Coon CBA FAQ:
Veteran extensions:
Extensions to contracts that are not rookie scale contracts (i.e., veteran extensions) may be signed up to June 30, the day before the player would have become a free agent.
For contracts with options or ETOs, the end date of the contract is interpreted as the June 30 before an option year, and the June 30 after an ETO year.
A team cannot reacquire a player they traded away during that season (a season being July 1 - June 30). If he is waived by his new team, then he cannot re-sign with his original team until the one-year anniversary of the trade, or until the July 1 following the end of his contract, whichever comes first. However, if a team trades a player's draft rights, they can reacquire the player during the same season.
Option years (except in rookie scale contracts and player options for players who will be restricted free agents) and ETOs must be exercised1 (see question number
59)
June 30:
Deadline to extend a qualifying offer (see question number
44)
Last day to sign an extension (see question number
60)
Players are credited with one year of service
Salary cap year ends
http://www.cbafaq.com/salarycap.htm