The logo was edited using inkscape using the Denmark font that is used by the main Boost logo. The Denmark font is not embedded in the source SVG "color_source.svg" and cannot be displayed correctly on platforms which do not have it. Therefore the svg version "color.svg" used in the docs and the README.md has the letters rendered as shapes.

It seems possible to manually embed the font, but this was not attempted.
https://graphicdesign.stackexchange.com/questions/43300/embedding-fonts-in-inkscape