Obviously, all open source editors come free of charge. These are usually in the category of the “Traditional Editors”.
The most popular open source editors with VHDL, Verilog and SystemVerilog capabilities are:
In addition, some commercial editors have “freemium” versions. These are free VHDL, Verilog and SystemVerilog editors, but the functions may be limited compared to the full version. Even with these limited functions, these free editors often contain more features than in the open source alternatives.