Apparently, the Rust Monster is in the OGL. It is also based on some cheap ass toy that EGG found in his travels, at least in appearance.
The Cease & Desist email that was this blog's topic yesterday was apparently in response to an illustration of a Rust Monster. According to the artist, it was his own piece of work: it wasn't traced or copied - apparently not even a homage.
So, if one draws a possible conclusion from this (requiring an "assumption" - and we all know where that can lead), WotC may be staking a claim that the OGL doesn't apply to images of elements that are covered by the OGL.
I really wish I knew the OGL better, but I'm not a publisher and I've only got one small article to my credit, so I'm hardly a writer, but if the OGL doesn't allow for visual interpretation of creatures described within, there's a whole lotta art that is in violation. The thing is, I don't think any of it would be in violation of copyright - but as my knowledge of such could fill a small shot glass, I'll leave such to those with more knowledge.
I do find the timing to be very curious.
The Space Gamer #83 -
3 hours ago