Hi to all,
I am the maintainer of the FidoCadJ project. I am happy to see that it has been cited here, since I am a big fan of EEVblog and I really enjoy Dave's videos (and BTW this is my first post here)
I can provide some partial answers about concerns expressed by Brumby.
For the server load, I believe that in ElectroYou the drawings are converted each time a new post containing one of them is posted. Then, the image is stored in PNG format in a cache and it is used as it is. FidoCadJ is a Java program and most part of the overload comes from the time necessary to load the Java virtual machine each time it is executed.
Concerning the security, it is something that has to be taken into account very seriously. First of all, you need to run Java on your server and this may be not allowed in some cases. That being said, the text format of files employed by FidoCadJ is quite restrictive: you just describe simple graphical objects (no file inclusion and no external access). The technique has been used with success on ElectroYou (and on Matematicamente) for several years and they did not experience security issues coming from that. However, nobody can be positively sure about a perfect security. It is part of the work of integrating FidoCadJ in a forum to make sure that the problems that an attack on it can generate may remain limited.
I am working only on FidoCadJ code and not on its integration with forums. I know that there is a vBulletin extension, but I do not know anything about SMF. I think the webmaster of ElectroYou inspired himself from the LaTeX vBulletin extension to implement it and we had a fairly usable implementation in a few days starting from scratch.
Finally, the official development site is not anymore on Sourceforge; we moved it on GitHub in August 2015:
https://github.com/DarwinNE/FidoCadJ(open source GPL v.3 project)
Hope it helps