They won't say how much money Dalton Maag is getting to make this really nice font without royalties, but it's assumed to be "lots and lots". Props to Shuttleworth for making free software worth professional designers' time.

Ralph Levien's Inconsolata [1] is the strongest attempt I've yet seen at reproducing the quality of TheSansMono.

[1]: http://levien.com/type/myfonts/inconsolata.html

Actually, Consolas is extremely similar.

Lucas de Groot, who designed TheSans, also did Calibri and Consolas.

http://www.lucasfonts.com/case-studies/calibri-consolas/

Consolas isn't free (although, at $35 it's not as painful a purchase as TheSans Mono Condensed).