Yes you have to unsling it.
However, seeing as Twonky doesnt seem to be supported anymore on the NSLU2 (not sure if this is all NAS devices) I would test the trial version first before buying.
I bought my NSLU2 and twonky after looking at the hardware/client thread poll. I'm now slightly miffed that despite the Linksys NSLU2 was by far the most popular server hardware, Twonkyvision/Packetmedia have decided to stop supporting it on that platform.
So much for "lifetime" license. Bit of mis-selling I think!
I'm still getting problems with my NSLU2 and MP101's. Streaming to XBOX is fine from the NSLU2 - but the MP101s skip and stop.
Running twonky on the PC is fine to both XBOX and MP101, however the whole point of running on the NSLU2 is so I dont have to keep the PC on all the time!!!!!