Incredipede on Linux is now absolutely free.
Incredipede developer Colin Northway says he made the Linux version free "because Linux users are such strong supporters of indie games," and because he enjoys its open source philosophy. Incredipede is available for Linux right here, and though it will run fine out of the gate Northway includes a list of tweaks to make it extra pretty.
Incredipede is also on sale on Steam for $5 through June 24. This is all part of an "Open Source Appreciation Week," and 50 percent of sales directly through Northway's Humble Store hub will benefit FlashDevelop and Box2D, two open source programs that he used to create Incredipede.