Came here to say this. In fact, I think every language that they give 5 stars to has some form of "foreign pointer", "raw pointer", "unsafe pointer" or the like that is nullable, for FFI and other low level tasks.

I think that anything which has no null in normal, idiomatic code, outside of "unsafe", "ffi", or similar subsets, should get 5 stars. The distinction is really about whether you need to worry about any possible value, or any possible reference, being null, which you do in languages like C or Java where all references are nullable.

Giving Java and Rust the same 4 star rating because they both have some form of null and some form of Maybe/Option is a bit misleading. In Rust, Option is what you use in any normal code, and so you don't need to check for Null everywhere. In Java, it's the other way around; nullable references have existed since the beginning and are not segregated in any particular way, while Optional is a recent addition.

Likewise, I think that in Scala and Swift, null is only present for compatibility purposes, and idiomatic code does not use them. I'm not sure about F#. Clojure does use nil idiomatically, and also has '(), which may even count as "multiple NULLs" according to this rubric, though I guess that in Clojure '() is just treated as an empty list, rather than a null value like it is in other Lisps.