I recently made a PR to remove unmaintained implementations from the
SRFI support table, in order to make room for new ones:
https://github.com/schemedoc/srfi-metadata/pull/54

Lassi suggested posting about it here, and also suggested moving
unmaintained implementations to their own section on scheme.org, which
was previously discussed here:
https://github.com/schemedoc/surveys/pull/53

I would like to propose the following criteria for what makes an
implementation unmaintained:
No mailing list or repository activity in 3 or more years, or the
maintainer posts a notice saying the implementation is unmaintained.

I am OK with unmaintained implementations having a separate section,
since the effort was already made to include them. But I think removal
would be better because the info is already tracked in source control
and can be retrieved if needed. Not a big deal though.

Thanks,
Antero