Liberation Sans is not equivalent to Tahoma but to Arial (the key word here is metric-compatible; means same dimensions, same spaces) :
Liberation fonts
From Wikipedia, the free encyclopedia
Liberation is the collective name of three TrueType font families: Liberation Sans, Liberation Serif and Liberation Mono. These fonts are metric-compatible with Monotype Corporation's Arial, Times New Roman, and Courier New respectively.
They are available under the GNU General Public License
I've found that FreeSans renders much better (with hinting and subpixel aliasing) that Liberation Sans does at sizes around 8pt. So - FreeSans better in some ways, think I'd vote against this one.
Bitstream Vera Sans is better than either IMHO, but not metric-compatible with Arial (it's "wider.")