IEC 61804-3 is available from the IEC at https://webstore.iec.ch/publication/22636. FieldComm Group does not license this document directly.
However, this document is a superset of the HART and FF (E)DDL specifications. The member can use those specifications to develop EDDs, but if members want the IEC version, the member would need to license it directly from IEC. For example, if members want to know more about PROFIBUS EDDs, then the IEC version would be appropriate.
FieldComm Group is working on a single EDDL specification/standard moving forward. In the next edition, the IEC and FieldComm Group editions will be closely aligned.