INDIE multi-user license

I already have Visionaire Studio license for single user, but I've brought one other person to help me out with the development. Is there some sort of upgrade of the license to multiuser or we must buy the multi-user license with full prize? 

thanks a lot for any notes or advice!

If they aren't touching the editor then they don't technically need a license, but to answer your question, unfortunately there are no upgrade options available, you will (at some point) have to buy the multi-user license, or get them to pay for their own indie single user license so that they can work on their own game projects too later on, if they want.