Um ...
Since they are on their respective team's roster, they legally CAN be traded.
But this deal will obtain a "waiting till day 51" tag soon ...
No, It's fallen under that already:
http://kb.ssbabasketball.com/wiki/Trades_%28Rules%29#Who_Can.27t_Be_TradedPlayers signed can’t be traded for 60 days, unless they are traded in a sign and trade deal. Sign and Trade deals must be posted within 24 hours of the player being signed. Players given extensions following the playoffs (before the draft) aren’t subject to this rule and can be traded at any time. Players signed during the offseason can’t be traded until the date pursuant to the chart below.
Edward Priddy was signed on day 4 of FA.
The part quoted by the Hornets applies to players acquired in a trade, not signed through FA.