First a minor nitpick, why does the library declaration reserve an
explicit required parameter for the language, when there is currently
no way to write your own or specify alternate languages?  Even when
there is such a feature, in (imagine some fantastically huge percent)
of all cases people will use the default.

It seems to make much more sense to optimize for the common case and
use a separate, optional form to specify a language, such as Chez's
IMPORT-ONLY.  If you don't like the name because it sounds too close
to the ONLY import form, you can change it to LANGUAGE or
PARENT-MODULE or whatever:

  (library "foo"
    (language "scheme://r6rs")
    ...)

It's more descriptive too.

Also, I agree with the earlier post that strings are being abused
here for the names, and SEXPs would be the natural solution.

Speaking of which, something really needs to be said about the naming
convention.  Once you get people sharing modules you need a naming
hierarchy, unless you want to descend into CPAN naming hell.

Extrapolating from the default language, it looks like we can expect:

  scheme://srfi.schemers.org/srfi-1
  scheme://okmij.org/oleg/ssax

--
Alex