Every year, NBA teams give out non-guaranteed contracts to players on the fringe of their rosters. Typically, everyone who comes into training camp actually has a deal for the whole season, but $0 of that deal are guaranteed (the players get a training camp stipend for which there is no cap hit). Anyone who sticks, the team has complete control over: they can be kept up until January 10th and cut at any time for no additional cap hit. For every game a player stays on the roster, they're paid 1/82nd of their contract and that amount is added to their cap hit.
The January 10th deadline is a little tricky--players actually have to clear waivers by that deadline, meaning that any player would have had to be waived on the 7th to be eligible by the 10th.
When the Clippers entered the season, they had 14 guaranteed contracts and were forced to choose between Chuck Hayes and Luc Richard Mbah a Moute's non-guaranteed deals to carry for their 15th and final roster spot. Doc Rivers chose LRMaM (I'm calling him that now, I've been doing it for a while, and I'm not going to stop), and the rest is history: the only player on the team without guaranteed money has started 20 of the team's 36 games (the most of anyone outside of the core 4) and the 5-man lineup featuring LRMaM and the rest of the starters has a +11.6 Net Rating. That's not bad for the only non-guaranteed guy.
So, it's not surprise that the Clippers are keeping their new starting SF past this deadline, because even if his current role changes by the end of the year, he clearly has defensive utility for this team. It's pretty telling that a big date like this was coming up, and I wasn't even paying attention to it.
For now, the Clippers are moving forward with 15 guaranteed contracts, leaving them with minimal flexibility when the time comes for Doc Rivers' traditional buyout bin shopping. If such a move becomes available, the Clippers will have to open a roster spot through either a trade or by cutting guaranteed salary--not a tough pill to swallow, but a tougher pill to swallow than cutting someone for free, or filling an already-empty roster spot.