FreeHDL
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Project to develop a GPL VHDL simulator for Linux.
2.
GHDL
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A VHDL simulator and implements nearly all VHDL87 and some features of VHDL93. GHDL is written in Ada95 and it is a GCC front-end. [Open source, GPL]
3.
Leonardo Spectrum
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A synthesys tool, which will optimize your ASIC/FPGA/CPLD design. Evaluation license is available.