Installing the Twonkyvision server implies that you've upgraded your NSLU2 firmware to Unslung. So for the remainder of this article, I'm assuming that you've upgraded to the latest Unslung firmware, which as of this writing was 3.18-beta. If you haven't upgraded, then do it now, starting with the instructions here.
Additionally, I'll assume that you've followed the Unslung directions to enable telnet so you can log into the box, and that you can use the standard NSLU2 functionality to copy files to the NSLU2 hard drive. Once that's done, let's get started.
The initial step is to get the UPnP server. Twonkvision has two different versions available - a music-only version available for free, or a server that supports music, photographs and video you can purchase for around $20. I'm using the full-featured version and my instructions will be geared toward it, but the setup is the essentially the same for both.
Updated May 28, 2005
Since the article was published, Twonkyvision has changed the free version of its server. For embedded platforms such as the NSLU2 and the Linkstation, it now has a trial version of the media player instead of a free musicserver. This new version runs for 10 minutes and then quits.
In the new free version, the NSLU2 server resides in an "embedded/armv5b_333_225/" directory.
Visit Twonkyvision, and buy the paid version. Unzip the downloaded file and you'll find a number of subdirectories for the various supported systems. We're interested in the NSLU2 directory.
Inside this directory you'll find several files including the UPnP executable itself, mediaserver, plus the music-only version: musicserver. Along with the executables, the directory contains various README and install scripts. I looked the scripts over, and they may work in some cases, but I decided it would be better to install the server our own way to better fit into the Unslung environment.