Dear Unicoders,
please comment the following proposal which I plan to submit to the
Unicode consortium.
Werner
PS: At least two fonts families have glyphs for the copyleft sign: TC
(e.g. tcrm1000.mf, developed by Jörg Knappen; available as
METAFONT source files) and OmegaSerif (e.g. omseco.pfb, developed
by Yannis Haralambous; available as Type1 files).
Any modern TeX package comes with these fonts.
======================================================================
Inquiry
-------
When implementing Unicode features in the groff type-setting package
it became apparent that there is no Unicode character for the copyleft
sign. This symbol denotes free software compatibility and is used
analoguously to the copyright symbol.
There is a common effort of free software developers to submit the
existing glyph as a Unicode character. This submission inquiry is
based on a discussion in the groff developer group and is supported by
Richard Stallman, the president of the Free Software Foundation,
Inc. and other members of the FSF.
Rationale
---------
In many areas related to computation, there is an increasing interest
in free software products. There exist several free software license
schemes tailored for different applications. The copyleft symbol is
intended to denote that a document conforms to one of these licenses.
The exact usage conditions for the copyleft sign have yet to be worked
out, but possible candidates include the GNU Public License, the Free
Documentation License, the BSD License, the Artistic License, etc.
Note that not all `open source' software is automatically free
software since the software licenses are often too restrictive, and
the copyright isn't `left' to the user.
As the major computing industry is shifting toward free software --
e.g. IBM, SGI, Corel, and many others -- the free software licenses
will become even more important than they are already. After some
years, the copyleft sign might be seen almost as often as the
copyright symbol.
Glyph
-----
The GNU COPYLEFT SIGN is a reversed copyright sign. Its glyph is
constructed by mirroring U+00A9 (COPYRIGHT SIGN) about its vertical
axis.
Character
---------
The GNU COPYLEFT SIGN character would fit in the LETTERLIKE SYMBOLS
section U+2100-214F. Its Unidata entry can be adapted from U+00A9 and
will read
21xx;GNU COPYLEFT SIGN;So;0;ON;;;;;N;;;;;
Existing similar characters
---------------------------
There is a Unicode combination that is similar to the intended
copyleft symbol,
U+2183 (ROMAN NUMERAL REVERSED ONE HUNDRED) +
U+20DD (COMBINING ENCLOSING CIRCLE)
but this combination is logically unrelated to the meaning of the
copyleft symbol and the proportions of such a combined glyph seem to
be different from a reversed copyright sign.
The rotated C used as U+0186 (LATIN CAPTIAL LETTER OPEN O) is not
suitable for constructing a copyleft character.
U+24B8 (CIRCLED LATIN CAPITAL LETTER C) looks like a candidate for
reversion, but for logical reasons, reversing the copyright sign is
preferable.
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