What legal data can FO output that would be meaningless to GEDCOM?
Certainly FO outputs syntax that has meaning to GEDCOM. However, the grammar may not be understood by other conforming GEDCOM compliant programs. I would not recommend using some tags for this reason. STILLBORN generates a generic event type data in GEDCOM while the standard wants this information in an AGE construction that FO doesn’t support or understand. Similarly AKA should not be expected to be understood by another program although the information will be preserved for interpretation by the human reading the data. Depending on what you meant when you used AKA it might be a nickname or an alternate name for the same person. A nickname is defined in the GEDCOM name structure but not supported this way by FO 6 or 7. If you meant an alternate name for the same person such as an adopted name GEDCOM defines that the NAME structure be repeated but I doubt that many existing programs would properly interpret this.
