They can play pick up games like they do in the summer. No coaches allowed until the season starts.
A few items from NCAA bylaws relative to practice and related activities:
1. Official practices can begin 42 days before the first game - but only five days per week. A few non-practice activities are allowable before then (see #'s 2 and 3 below), but most normal practice activities are not allowed at all (see #4).
2. "Team conditioning or physical-fitness activities supervised by coaching staff members may be conducted on or off court but shall not begin prior to the beginning of the institution's academic year."
3. "Outside of the playing season, from the institution's first day of classes of the academic year, only a student-athlete's participation in required weight training, conditioning and skill-related instruction shall be permitted. A student-athlete's participation in such activity shall be limited to a maximum of eight hours per week with not more than four hours per week spent on skill-related workouts."
4. "Prior to the start of on-court preseason basketball practice (i.e. the practices that begin 42 days before the first game), members of the institution's coaching staff may not be involved with one or more team members at any location in any of the following activities: (a) Setting up offensive or defensive alignments; (b) Chalk talks; (c) Discussions of game strategy; (d) Reviewing game films or videotapes; (e) Activities using basketball equipment; or (f) Observing student-athletes in any basketball activities even if such activities are not arranged by the institution's coach." (Note: certain activities enumerated in #2 and #3 are permissible.)