FOSTEX Wave Manager supports only one type of their proprietary files, that generated by the Fostex MR series Multitrackers. Those with the original MR-8 needed to update their firmware to 1.08. The app is 32 bit but the current version was updated to run on Intel as well as PPC — no system requirements are listed.

FOSTEX WAV Manager

If the manual is to be believed, you may have to import them from the formatted CF cards but there may be a way to trick that. I converted my MR-8 files on import years ago. CF card readers are easy to find on Amazon if needed.
WAV Manager Manual

Unfortunately, other FOSTEX digital compression formats such as that used by my FD8 are unsupported and there's no conversion app that I know. Fortunately, I had selected 44.1/16 .wav back in the day and never had to deal with that.

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