sijad Don't think it's possible.
I wouldn't consider it their "real username" as much as their login name.
It also has a minor security risk. Knowing this allows users to attempt to login as you.
Steam provides two things to mimic what a unchangeable username provides
If you want it to be wholly unique to a user, you should use their steam id. But a long sequenced number isn't very appealing!
If possible, default to a steam profile name and give the option to change it as desired?
