Ecofont is an open source font designed as a way to save ink in printing, which is supposed to help the environment.
Here are some questions from the Ecofont FAQ, which I assume was written by someone whose first language is not English. The first answer is especially illuminating:
How can Ecofont be free?
We do not have to make a profit out of the Ecofont.
The letters are not really clear on my computerscreen.
The Ecofont works best when font size 9 or 10. The results vary depending on your software. If you work on a Windows platform you could use ClearType.
When I print the font, it looks as if my printer is running low.
The print is somewhat greyish because less ink is used.