Hi, It was all done with in-game scripting using Lua code and our API:
http://lua-api.factorio.com/latest/
Hi, it is public beta at the moment, you can opt-in through Steam
We use our modding API to script all the movement in the trailer:
http://lua-api.factorio.com/latest/
We have many plans for what to do after version 1.0 :)
Yes, conversions are always possible. It might require to change some parts of the Factory, but usually not much.
There is not a big difference between the saves, you can just load multiplayer save in singleplayer.
The minimum for the game is 512 Mb of dedicated video memory.
Yes, we use phpbb, which is 3rd party free forum software. We don't plan on rewriting it, as you said, developing the game is more important.
This is probably solved in 0.12.