The Linksys NAS200 is another network-attached-storage box from Linksys, with space for two internal SATA hard drives. You can find more information about it at this page on the Linksys website.
The review at http://www.smallnetbuilder.com/content/view/30127/75/ indicates that is has *lower* performance compared to an NSLU2.
First up how to take it apart!
Okay not so fast, first lets not void the warranty before turning it on.
It defaults to DHCP. well, it turns on, but web manager login doesn't work; probably because there is no disk installed. okay! Now to disassemble.
1/ using a putty knife, carefully pry off the bottom silver cover. This will reveal 4 screws.
2/ Remove those screws to reveal a similar arrangement for the upper drive bay.
3/ Again for the PCBA housing.
4/ Four screws holding the PCBA to the upper housing.
5/ JP1 is serial, using the same pinout as the NSLU2. It talks at 38400.
Since the CPU is a RDC R3210-G, one would hope the RDC port of OpenWRT will work.
Linksys has also published the GPL information for the Linux version it uses on their GPL Code Center.
Discussions about porting OpenWRT or any other firmware to the NAS200 should take place at the appropriate mailing list.
Having a quick poke around, it appears it's running Twonky Media Server.
Connect on port 9000, you'll notice the twonky icon in your URL, then put /configpage/TwonkyMediaConfig.css and you'll get an access denied page, any other url ie "oops" and you'll get a 404 page.