invites.js

var communityName = Settings.get('title','Telescope'),
          emailSubject = 'You are invited to try '+communityName,
          route = user ? Telescope.utils.getSigninUrl() : Telescope.utils.getSignupUrl(), // this the line I added
          emailProperties = {
            newUser : typeof user === 'undefined',
            communityName : communityName,
            actionLink : Telescope.utils.getSiteUrl() + route, // site url + route depending if the user already have an account or not
            invitedBy : Users.getDisplayName(currentUser),
            profileUrl : Users.getProfileUrl(currentUser)
          };