* "In 1972, Cal Daniels completed the first demonstration version of the Xanadu software on a computer Nelson had rented for the purpose
* "While at Autodesk, the group, led by Gregory, completed a version of the software, written in the C programming language"
* "Then a newer group of programmers [at Autodesk] used the problems with this software as justification to rewrite the software in Smalltalk"
From the Xanadu website, regarding their demo XanaduSpace: "The enthusiastic and talented programmer, Rob Smith, of Manchester England, did a beautiful job combining a lot of our ideas [...] John Ohno and Jonathan Kopetz, in Connecticut, spent several years trying to refactor it, but it's beyond fixing-- though as a demo it works just fine."
The related ZigZag project: "The first prototype consisting of two character-graphical views was implemented as a Perl module by Andrew Pam in 1997", and there's a more current implementation by some other people( https://sourceforge.net/p/gzigzag/_members/) called GZigZag
If I had been trying for NEARLY 60 YEARS to get a software project out the door, I would have probably started trying to code it myself after the first decade or so! Every time Xanadu comes up, I'm consistently puzzled at how there's never any sign of Nelson actually doing the grunt work of implementation!
Edit: here's an interesting link from the ZigZag wikipedia page, where a GZigZag implementor talks about their experience (http://lambda-the-ultimate.org/node/233#comment-1715):
> The GZigZag project did not materialize Ted's dream system as fast as he liked, so he withdrew his support. At first it just meant that he wasn't participating in discussions as much as he used to. At some later time he asserted his trademark (he had earlier given his permission to use it), and we changed the name to Gzz. Around the same time I was burning out, partially due to Ted's distrust and a large part due to project internal chemistry problems. I bailed out on the project in the end of 2002.
> Some time after my departure from the project, Ted asserted his ZigZag patent. The project was forced to abandon all ZigZag related stuff; it was reformed as Fenfire by salvaging those innovations that were not inseparably linked to ZigZag and using RDF as the new core. I hear that's not the last bit of trouble from outside parties the project has run to, but I cannot discuss even the little that I know in public. Suffice to say that even Tuomas burned out on the project eventually.