In Metrilo, you can add as many team members as you want at no extra charge.
To invite someone, simply do the following:
Go to Settings and click Team.
Enter the email address of the person you want to invite.
Click Invite. An invitation will be sent to the email provided right away.
When the person receives the invitation, all they need to do is:
Accept the invitation by clicking on the Accept invite button in the email.
It will lead them to the Create an account page in Metrilo. They fill in a name and a password and they're done.
Note: If you want to invite teammates to more than one project, do it from one project first so they create an account, and then just add them to the other projects. This way, they will be automatically added with their existing account.