I was traveling for work for 5 days and nearly missed that PlayOn has pushed their Roku 2 patch out to the world. From the PlayOn forums:
Yes, we have included the Roku 2 patch in the most recent build of PlayOn. You should not need to use a different version now.
Thank you for using PlayOn – We appreciate your support!
It appears in version 3.14.14 and later. I’ve tried it out on my Roku 2, and it works great.