The Manual
« Section 5 »
5.1 Users
GlotPress uses the WordPress user table which makes your WordPress users GlotPress users as soon as you install it. This means by default anyone who has access to your WordPress site will have the ability to submit (but not approve) translations. Due to this you may want to create a new WordPress install dedicated to your GlotPress install.
However GlotPress does not use the WordPress permissions system (Roles) due to the complex nature of permissions in GlotPress. For details on setting user permissions, please see section “6.8 Project Actions” for more details.
GlotPress users also have some additional settings specific to their GlotPress profile, please see section “6.13 Your Profile” for more details.