One certainly gets the sense that modding is... barely tolerated, let alone encouraged.

Any scraps of examples or information is usually out-of-date and from 2012 (and, usually, written by the community anyway), and anyone who actually knows any answers are either behind NDA, don't leave documentation after leaving the community in frustration (fair enough) or barely struggling to get by themselves.

Take for example the 3DS-2014-only modelling tools, which is hard enough to get hold of as a trial, and impossible to buy, now. Aerofly FS2, a new property from an undeniably smaller company that had unexpected popularity, just released their SDK tools: It supports 3DS 2012,12,13,14,15,16 and Cinema 4D, which whilst none of them free at least includes available software.

I've actually seen people arguing that it is a good thing that they are so closed off about modding because then you would have "lots of low quality mods", and "non-serious mods" whereas I really believe a modding community thrives on it's breadth - both as examples of the crazy things people can do, and because otherwise the really skilled people aren't going to bother pushing so hard against the tide.