In the abstract it clearly mentions - "OpenTimer works on industry
formats (e.g., .v, .spef, .lib, .sdc) and is designed to be parallel and
portable. " I don't find VHDL.
Moreover it comes from an American University, a country where Verilog is the dominant RTL language.
It is better to ask the author for details as I don't think this tool has industrial acceptance yet.