Well, IANAL (I Am Not A Lawyer), but as far as I can see, any "Manny"-model is clearly a derivative work of the original Manny-model (same goes for the rest of the models and textures etc).
This puts it in what I think of as a grey area, but then again, there are quite a few cases of fan-made "High Resolution Packs" for various games out there (Duke Nukem 3D might be a decent example). I think that you'd be more in the clear if your data was .patchr-formated, as then the data would be clearly dependent on the original data files (and not for instance a solution similar to the OpenGFX-files for OpenTTD, which aim to replace the need for original game data).
Now, the original game did support any amount of data???.lab-files with higher numbers getting higher priority, the only adjustment we did in ResidualVM was to add a "datausr.lab" which had "the highest priority, even above the patch". This is for now the main extent to which we support any user-patching of the game data (but there might be nothing preventing us from for instance making the texture-loader look at file-formats instead of which game is played to select the files to load, and thus be able to load 24 bpp TGAs instead of MATs).
However, preferably, there should be atleast some divide between the two projects, as ResidualVM aims to be a game-engine for the original data (game data which we need to be rather carefull not to share), while Grim Fandango Deluxe aims to improve upon that game data, and thus is rather required to share derivative works of that data. So, in MY opinion (not to be confused with any consistent view among the other devs, as I have not talked to them about it), you should probably set up some web page separate from ResidualVM for the actual "show-and-tell-and-share"-part of your project (similar to the talkie-monkey-island-stuff). Perhaps you could approach Mixnmojo about it?
All that being said, Lucasarts has had a tendency to not care so much about their old IP of lately (but they also tend to change their minds quite often), which means that right now they might not care. Still, they are not as relaxed wrt it as for instance Sierra has been. (OTOH, the Zak McKracken 2 guys are still alive and well, but they did go the route of "keep the characters, but make entirely new assets").
Hope this clears up something, and as I said before, I quite appreciate your work.