Kernel Mode Linux is a technology which enables the execution of user programs in a kernel mode. In Kernel Mode Linux, user programs can access kernel address space directly. Unlike kernel modules, user programs are executed as ordinary processes (except for their privilege level), so scheduling and paging are performed as usual. Although it seems dangerous, the safety of the kernel can be ensured through such methods as static type checking, software fault isolation, and so forth.
TOS is an operating system kernel that is written in a strictly and statically typed assembly language. Traditional operating system kernels are written in weakly-typed languages (e.g. C, C++). Therefore, it is extremely hard to ensure safety of the kernels. On the other hand, memory safety and control-flow safety of TOS can be ensured automatically through the type check of the language.