First name, last name

[Takeshi]

On Exlis, the first name and last name are required. Is there any possibility to make this fields not required and use only the username?

[rentasite]

I don't think you can make them "not required". But of course you can use only Usernames. From your Elxis site administration panel:

Settings > Users and Registration > Display users as

You will find 2 options: First Name Last Name & Username