SUNDAY, 11:35am: The Celtics officially announced Williams' multi-year deal in a press release. The team didn't disclose financial specifics, but Mark Murphy of the Boston Herald reports the contract includes triggers that would guarantee the deal for next season in stages.
FRIDAY, 2:52pm: Wojnarowski confirms that the contract is for the minimum salary and that it isn't fully guaranteed for 2013/14.
2:01pm: Terrence Williams' 10-day contract with the Celtics is set to expire after tonight's game, but Boston will re-sign the former 11th overall pick for the rest of the season, reports Adrian Wojnarowski of Yahoo! Sports (via Twitter). According to Wojnarowski, the Celtics will also sign Williams conditionally for 2013/14, which I assume means '13/14 won't be fully guaranteed.
Williams was one of three players signed to 10-day contracts by the Celtics after returning from China. D.J. White and Shavlik Randolph, who also spent the season in the CBA, are expected to be in uniform for the first time tonight. So far, Williams has appeared in three games for the Celtics, including playing nearly 25 minutes last Friday against the Suns, recording nine points, four boards, and four assists.
When Williams' contract becomes official, the Celtics will have 13 players on guaranteed contracts this season. For next year, Boston currently has 10 players on fully guaranteed deals. Paul Pierce also has a player option, while Williams will presumably have either a non-guaranteed or partially-guaranteed deal.
As I detailed earlier this week, the Celtics are already projected to be taxpayers this season. So even though Williams' contract will almost certainly be for the minimum salary, it will cost Boston twice as much as usual, once the tax penalty is considered.