You can participate if you are a Linux user in Progress Thru Processors.
The simplest thing to do is this:
- Go to http://www.gridrepublic.org and sign up. Specify Linux as your platform. Follow the instructions.
- When done, go back to Facebook and add the application: http://apps.facebook.com/processors/new.php
- In the first question on the registration page, check "No, I am a GridRepublic user", enter the e-mail + password you used in step #1 above, and then follow the on-screen instructions.
GridRepublic seeks to improve the process for Linux users in the future. Hopefully, this can get you started.