Free Forth systems are bad for Forth.

"Anyone can write a bad Forth and give it away without documentation or support; after trying such a system, nobody wants to work with Forth anymore. Free Forths give Forth a bad name. Free Forths take business away from the vendors." "Many people learned Forth with fig-Forth. There are good free Forths. Most successful languages started with (and still have) free implementations. Languages without free implementations (like Ada, Eiffel and Miranda) are not very popular [There are free Ada and Eiffel implementations now]."