Via their official site, the Pirates have outrighted Deolis Guerra and, apparently, Travises Snider and Ishikawa. Snider and Ishikawa have elected free agency. Guerra has officially been sent to Indianapolis, although he should now be eligible for minor-league free agency, so it wouldn't be a surprise if he ended up going elsewhere.
None of these moves are particularly surprising. The Pirates treated Snider and Ishikawa as depth pieces down the stretch. They were both arbitration eligible and would have made more than the big-league minimum next year, so they were pretty likely to be outrighted or non-tendered at some point. They'll now be free to catch on with other organizations, likely on minor-league deals. It would be good if the Pirates could make sure Guerra sticks around next year, though -- he shouldn't break camp with the big-league team, but he was terrific at Indianapolis in 2015 and is great minor-league depth.
The Pirates currently have 37 players on their 40-man roster, plus five who are on the 60-day DL.