Cathal,
No worries -- it's just giving me incentive to continue to improve my own skills. 
In the meantime, though, I've corresponded by email with Dario Solera of ScrewTurn Software. He wrote:
As far as I know, there are a few users who integrated the application in an instance DNN by basically adapting the look and feel and integrating the authentication providers, but they did not build a DNN module. You might want take a look at the following forum thread: http://www.screwturn.eu/forum/viewtopic.php?f=12&t=4503&p=8876
Following the thread, a colleague on the forum wrote:
All,
I've read a few discussion here about people interested in integrating their ScrewTurn Wiki with DNN. I'm happy to report that I've successfully implemented a plugin that can authenticate DNN users to ScrewTurn. The plugin only alows authentication. All other user features are disabled as the provider is readonly. It works well for what I wanted to do. Maybe someone else can take what I've done and extend it.
I bring this up because I'm willing to share my source and setup if anyone is interested. I'm not interested in providing and supporting a pre-built plugin though. I'm not really sure of the proper way to share source on these forums. I can provide a download or whatever. Just let me know.
[DNN 4.8.4]
http://www.jasonnewell.net
[ScrewTurn 2.0.33]
http://wiki.jasonnewell.netHe then provided the source, downloadable here: http://www.jasonnewell.net/Public/ScrewTurn/ScrewTurn_DNN.zip
I don't know if this will be helpful for you or others, but I thought it was worth posting, in case it is.
Steve