So far I've only downloaded the macOS version of the code (see source website: https://www.mamedev.org/). It's a bit of a faff but it doesn't involve compiling in my case (macOS). I just pulled out the castool file and started using it on the command line.
Here's a list of all the conversions castool can do:
https://docs.mamedev.org/tools/castool. ... l-for-mame
I successfully converted a FORTH.tzx file to FORTH.wav and copied it to tape, loading it successfully with LOAD "" CODE on my ZX Spectrum+ and Spectrum +3 (using tape input).
Web site down, but ...
https://web.archive.org/web/20180808183 ... wintzx.fr/
http://www.worldofspectrum.org/pub/sinc ... ZX0.9a.exe