In November a Mark Schonewille posted a blog on when you can't and cannot use the GPL version of MySQL together with your closed source application. The post was a result of actually talking to an Oracle lawyer which makes it valuable information. Unfortunately Mark's blog is now offline (it seems he didn't renew his domain registration?)
This is just a repost of the disappeared blog post. (The small print allows me to copy it verbatim.) There is no commentary from myself, except that what Mark wrote is the same I also heard Oracle say a year ago. That Oracle is being consistent on this point is very welcome and deserves to be kept available online.
Update 2011-06-23: Mark comments that his blog is still online, but at a new address: https://qery.us/tl