Many sites (including openqnx) reported the official release of QNX 6.2.1 NC in the past. Some users have been questioning whether it is really official. It is real this time. The official download URL is http://download.qnx.com/d_manager/d_man.php
Admin Updates:
cksum qnxnc621.iso 179511721 248741888 qnxnc621.iso
md5sum qnxnc621.iso 0489c116af49f3aca814df33a6a3e13e qnxnc621.iso
see Comments for mirror sites