Just got word that it's still an issue in 4.50.0.0. Pathetic!
At this point the only workarounds I've come up with are:
1. Create a ""required"" drop-down UDF with users' names, for the user to pick their name on each invoice they create. Only problem is that there's nothing preventing them from selecting the wrong name. OR
2. Create a ""locked"" UDF to store the user's name along with a Script that auto-populates it based on the MAS 90 user logon - and have that data flow to history. (It doesn't appear standard functionality can accomplish this, e.g., Business Object UDF or via the Data Sources tab in UDF Maint).