I believe that is still considered open source, just not Free, Open Source Software (FOSS). It's basically one point shy of the GPL in that you can't redistribute the source, but modifications are allowed. I believe they even take contributions.
Open source doesn't depend on whether you pay for it.
The OSI definition of open source (which was the original coinage) requires that users be able to redistribute the source. Companies have been licensing the source to game engines for ages, but that's not open source.
Open source doesn't depend on whether you pay for it.