A few weeks ago Red Hat released the Liberation typographic family, saying that the fonts would be metrically identical to the famous Arial, Times New Roman and Courier New, distributed by Microsoft. In practice, a document formatted with Arial could be displayed with Liberation Sans without any distortion. Really?
With the new version of GNOME Specimen, a font previewer for GNOME, I decided to test if the Liberation fonts had the same size as the Microsoft ones:
Indeed, given the same height the Liberation fonts have the same width as their proprietary equivalents. However, the fonts are quite different, for example in weight and x-height. Only Liberation Sans is similar to Arial, which in turn is an imitation of Helvetica. Liberation Mono seemed to be more legible than Courier New, and Liberation Serif, even if as compact as Times New Roman, is more pleasant because of its lightness.
In sum, the Liberation fonts fulfill their task of substituting Arial, Times New Roman and Courier New, whithout losing their own identity. Free software scores again!