Since the application user name in Altru is pulled from the user's Blackbaud.com account the name would need to be changed on Blackbaud.com. Once that name is changed on Blackbaud.com it should change in Altru within 24 hours. 

To change the name in Blackbaud.com
  1. Go to http://www.blackbaud.com and login
  2. After signing in hover over your name and click Blackbaud ID profile
  3. Click edit personal details > edit your name
  4. Click apply changes