Well, last night I stumbled across SuperTweet. It's a Basic Auth -> Open Auth proxy. It's specifically made for devices or code, for whatever reason, can't or haven't been updated to OAuth. If you want a simple, straight forward interface for Twitter, this is it. It's brilliant. Why should you care? Well, you can now use the precious `libpurple-twitter-protocol` plugin with it. Here's what you do;
Go to SuperTweet, get an account and authorize it to Twitter. Install `libpurple-twitter-protocol` from extras-devel. Create a new account, scroll down and select Twitter. You'll enter your username and the supertweet password you used. Hit "Advanced" and (unfortunately, you'll need to) uncheck the HTTPS option. This means your credentials and all data is sent in plaintext. When configuring the Twitter plugin on your N900, simply change the Host URL and Search URL to "api.supertweet.net"
Set your refresh rates and you're done. Everything works like it used to before they 86ed us and boy is it glorious!