Scala is a pretty well known language and it has a very active core team. Researchers, Scala Center team and other people made it their job.
I wonder where the required income to pay everyone and maintain Scala comes from? Is it generated by Scala through instances like Lightbend or maybe sponsorship? Do revenues come from other EPFL works?
PS: I am not sure this is the right forum to ask this question but I struggle to find a better place.
Martin Odersky is a professor at EPFL and basically devotes all the time he has besides his duties to Scala. This is similarly true for many of his PhD students.
The Scala Center is mainly financed by its members, its MOOCS and by donations (scala.epfl.ch/2022-01-28-january-28-2022.md at main · scala/scala.epfl.ch · GitHub). Spread the word to organizations that profit from Scala (Corporate Membership) 
A large number of individuals contribute immensely to Scala in thier free time (Scala 2 and 3 compilers, the standard library, improving tooling, writing documentation and books).
The vast ecosystem of open source libraries only exists thanks to the countless hours that people pour into it in their free time.
Lightbend and VirtusLab are sponsoring engineers to work on open source Scala. This can also be said about JetBrains’ work on the (open source) Scala plugin for IntelliJ.
I’m pretty sure this is incomplete, I apologize…
This is already informative. Thank you for your answer.
Doesn’t Lightbend have sponsors too?
No, Lightbend is a private for-profit company