As has been noted, the CJ family is certified for single-pilot operations, but the type certificate calls for a "minimum crew of one"...doesn't mean there ONLY has to be one. In fact, two 525s-rated pilots may crew a CJ with one logging PIC and the other logging SIC and that would be 100% legal because even though the minimum crew MAY be one per the type certificate it doesn't mean you HAVE to operate with just one.

My company has a CJ2+ on order so I was VERY confused by all this to until it was explained to me by a very experienced CJ mentor pilot.

That said, if you log SIC in any aircraft you'd better have a 61.55 endorsement in your logbook to accompany those entries.