Purpose of this page:
Provide pointers to security-related informations that show Tcl is doing the right thing.
Sarnold: although lots of system applications are written in C/C++, we can consider that writing a new application in these languages is a lot more work, and lead to security holes.
And scripting languages are now strong, so according to Ousterhout's Dichotomy, we should write in C/C++/Java the critical part of the application that cannot be written in a scripting language, or would be unbeareably slow.
The rest of this page is trying to compare Tcl security against other programming languages to serve Tcl marketing. (Of course, we will exclude C/C++/whatever compiled language from this comparison)
About safe interps: it is a feature missing in almost every other language (Java has a similar functionality, but with such complexity that I cannot even think of it).