The translater can be written in high level Forth, and is largely portable, except for the target architecture sections. These are not shareware tools, and were written to support a portable binary system. It is described in the EuroForth'95 paper . Some people find the way THEN is used in Forth unnatural, others do not. Forth's THEN has the meaning 2b, whereas THEN in Pascal and other pro- gramming languages has the meaning 3d.
Threaded code is a way of implementing virtual machine interpreters.
You can find a more in-depth explanation at . There is no direct support for unsigned quantities. This doesn't match Forth's model too well. There is no such thing as pointer arithmetic. This is a security issue.