We had heard back in May that Rovio was going work on optimizing Angry Birds for the Lumia 610. While it may have taken six months to accomplish, it is our understanding that Rovio has optimized all versions of the Angry Birds games to work with the RAM memory limits of the Lumia 610.
There was no information available on how soon the Angry Birds titles will become available. We are still seeing Angry Birds as "unavailable for your device" on our Lumia 610 and it still may take some time to see the optimized versions show up in the Store. If you're using a Lumia 610 and are seeing the Rovio titles becoming available, chime in below in the comments.
Now if we can only get the Hoth Chapter for Angry Birds:Star Wars released...
Source: nokiatweet; Thanks, sammy, for the tip!