This would be the perfect opportunity to send them an email that you were able to get it to work on your OS and browser of choice.  Confirm that it works and share any bugs you find.  OSS or free, this still needs to be done.  Who better to check this out than a geek with a clue?

From: Don Ellis
Sent: Friday, March 30, 2007 11:07 AM
You could set your browser to lie about what OS (and browser) you're using. However, this skews the results to indicate your preferred setup is not as popular as it really is.

This kind of message is really infuriating, especially so when you can switch your non-standard setup to bypass the warning and it performs perfectly.

--Don Ellis