Q:

Typefaces with specific legibility characteristics & licensing

Are there any typefaces possessing all of the following characteristics?

Vox-ATypI classical, modern, or glyphic
I, l and 1 mutually distinct & identifiable without reference to each other
rn and m very mutually distinct
a and o very mutually distinct
single-storey g
lining numerals
not monospaced
available under an FSF-approved font license.

If so, which one(s), and how did you find it/them?

A:

Just to get this off the unanswered list, and since my comment appears to have been useful:
Most of the actual typographical requirements listed in this question will be matched by most fonts on the market; there are just one or two deal-breakers that are largely type-dependent:

Serif fonts rarely have single-storey g’s (except sometimes as an alternate)
Sans-serifs frequently don’t distinguish l/1/I clearly
Slabs frequently either have no single-storey g or do not distinguish l/1/I clearly (or both)

Single-storey g’s are very rare in serifs, though, while sans-serifs (and slabs) that distinguish l/1/I clearly are more common, so they’re an easier option to look for.
Really, the licencing may prove to be the tougher nut to crack here, since fonts licenced with an FSF-approved font licence make up a rather small part of the total number of available fonts.
One that may fit your needs is Andika by SIL. Its licence is FSF-approved and it matches all the typographical requirements (though I’m not sure if the single-storey g is an alternate or not).

