If you're an operator required to carry charts (121, 135, etc -- and if you don't know, you aren't), any electronic chart system you use must be FAA-approved specifically for your operation. If not (plain vanilla Part 91), the FAA doesn't much care what you use as long as you stay out of airspace in which you don't belong and don't get lost enough to run out of gas or, if IFR, deviate from your clearance -- and if you do any of those, the currentness/approval of the chart you're using will only affect the length of your suspension, not whether you eat a violation.
