This is GPL'd URW++ Nimbus Sans and Nimbus Sans Narrow fonts. It's a close relative of Helvetica/Arial/etc. This particular set has slightly modified vertical metrics to make it align properly under GNU/Linux.

Specifically, "Win Ascent" and "Win Descent" were decreased/increased respectively by 44 points. Additionally, "HHead Ascent" and "HHead Descent" has been assigned corresponding values from "Win..." counterparts, and "HHead Line Gap" has been set to "0".

All of the above has been modified using FontForge, under Element -> Font Info -> OS/2 -> Metrics dialog.