While the licensing of Ubuntu's new open font is still being discussed ... it's interesting to note that the Wikimedia Foundation, as part of the new improved style of Wikipedia, has made the decision to switch the font used in the lettering of the famous puzzle globe logo to the Linux Libertine open font. You can see that the upstream authors made a dedicated font feature for the distinctive stylised crossing of the W.
If your project is libre/open then picking similarly unrestricted components to build your own visual identity does make sense :-)