The bugs I have are very rarely related with the type of a variable. They are incomplete/incorrect implementations of business rules. The type system doesn't solve that.

It doesn't until you encode the business rules in the type system. But in a well-designed language that's actually fairly easy.

The other point of the article is that dynamic typing makes code rot. I am not convinced that static languages do any better. Code rot is not a problem of the typing system, it's a problem with the programmer writing the code, or the environment he's in. Let's see what happens when he inherits a 5-year-old Haskell codebase.

Having done both, it's far easier to port an old statically-typed codebase to newer versions of its dependencies than to do the same for an old dynamically-typed codebase. Compare a Wicket upgrade (seamlessly smooth, and the compiler will catch anything you've missed) with a Rails/Django upgrade (batten down the hatches, hope you've got high test coverage, and even then you'll likely have something break).