Well, I just spotted a Linux SPARC glibc 2.3.2 build for 5.0.68 and put the twonkymediaserver file on my ReadyNAS NV+ media share (in a directory called a on the media share of my ReadyNAS).
I then ran killall -s TERM twonkymedia to stop Twonky
I then deleted the database directory contents from /webroot/Twonky/db/xxxx.view (xxxx determined by tree name) as replacing the above file will force a database rebuild (I found that out on my test NAS).
I then typed cp -i /media/a/twonkymediaserver /usr/local/TwonkyVision/ (and then y to confirm I wanted to over write the existing file).
Restarted my NAS and immediately selected a database rebuild; it now claims to have Twonky 5.0.68 running.
Not sure if anything has changed, but my NAS still works so there you go; it has even updated the twonkymedia-server.ini file text to 5.0.68 too! I'll check the rest later to see if any others have changed, however, changing this file in isolatuion certainly hasn't broken anything; yet (it's still building the database so it's looking good so far)
The file is attached below to save you having to find it yourselves.