Did you ever get an answer?
In the past, during versions like 4.1, 4.2 single developer local licenses exist, but since Outsystems has the cloud single developer licenses are over, I guess
Before version 8 you could ask for a Community Environment of OS and install it on-premises. It was a 30000 Software Units license with all functionalities (only limited to a 1GB of database) and you could use it for production servers.
Then the logic changed and you can have an almost unlimited Personal Environment for development, but have to pay for production servers. It is in the cloud so you can't call internal webservices.