Description of the logo:

size: 330x100px
font: Source Sans 3, 96px

math:
    size:    243x100px
    color:   ffffffff
    bgcolor: dc3912ff

js:
    size:    87x100px
    color:   202020ff
    bgcolor: ffffffff

To update the logo:
- install Source Sans 3
- open mathjs_source.svg in inkscape
- use use Path menu > Object to Path on the text and export to mathjs.svg