Actually there is a very old solution released to increase the lenght of usernames in Baan from 8 characters to 256 characters. Look it up in the infor365.com KB. I don't remember it of the top of my head.
When you apply this solution it changes the domain for ttaad200.user allowing over 8 characters for usernames. Once you apply it there is no going back. It will change the structure of the $BSE/lib/user file into three other directories $BSE/lib/user/u $BSE/lib/user/c $BSE/lib/user/r (for remote users) and your ufiles will no longer be in $BSE/lib/user but $BSE/lib/user/u