I suspect i don't need to say much about the open source DejaVu project. The link speaks for itself. "The" DejaVu "fonts are free as in freedom, and may thus freely be embedded".
What i 'm posting below is a recent attempt to design Greek glyphs for the serif version from scratch, initially for my very personal use (i guess i liked too much typesetting in the Latin version). The idea of including these glyphs in the original DejaVu Serif is currently under consideration by the team running the project, so, your feedback on the way the glyphs look and any ideas for their potential improvement are more than welcomed.