From the San Francisco Chronicle:
Spillman signed: The Niners signed exclusive-rights free agent C.J. Spillman to a one-year contract. As a result, under the terms of the collective bargaining agreement, Spillman can't practice with the team until Thursday when the new league year is scheduled to begin.
Because of confusion over the new CBA rules, Spillman practiced with the Niners on Friday. The team immediately reported Spillman's participation to the NFL and was cleared of any wrongdoing.
Read the whole article here: http://articles.sfgate.com/2011-07-31/sports/29834932_1_spillman-training-camp-practice