Yes, you can invite others to create an account on the app. From the contacts screen accessed in the Chat or Pay section of the app. From the Pay section launch the contacts screen by tapping on the "view all" option under People, tap on the contact's name and  tap on the "Invite to Sasai" option. From Chat, you can click on the new Message icon at the bottom of the screen to access your contacts.  You can also launch the contacts screen by clicking [here].