Why are Metric Compatible fonts not copyright infringement?
<p>Metric compatible fonts (typically open-source) copy certain metrics from a (typically copyrighted) "source font". "Advance width" at least, and maybe other metrics (I have seen discussions of copying kerning data). Why is this not copyright infringement? Presumably the designer of a metric compatible font is not printing the source font and measuring it. They are using the <em>exact</em> metrics to achieve exactly the same horizontal spacing.</p>

<p>Why does the creation of a metric compatible font not constitute copyright infringement? </p>

<p>It is important to distinguish between</p>

<ul>
<li>a typeface, which describes the visual appearance,</li>
<li>a font, which may be interpreted as a computer program implementing a typeface, and</li>
<li>the name of the font.</li>
</ul>

<p>These aspects may be subject to different immaterial rights.</p>

<ul>
<li>The name may be subject to trademarks.</li>
<li>The font may be copyrighted.</li>
<li>The typeface may be protected by copyrights or design patents, highly dependent on the kind of typeface and on the relevant jurisdiction.</li>
</ul>

<p>A copyright for typefaces is not generally desirable, because this copyright would extend to all documents set in that typeface. Therefore, the U.S. doesn't acknowledge copyright for typefaces. Germany distinguishes between artistic typefaces (eligible for copyright) and utility typefaces (not eligible).</p>

<p>If a typeface is not protected, it is possible to create a new font under a different name that implements the same typeface. This is an extremely common practice. E.g. the popular Helvetica font was cloned multiple times. Arial is heavily based on Helvetica but differs in a few details. Arial was in turn cloned as Liberation Sans. The TeX Gyre Heros font is closely based on Helvetica. </p>

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