Thanks a lot for the support !
Also thanks to everyone for pointing out the Counterparty Protocol. I had actually been following them when they launched, but I had quite a busy month, lost track of it and never got around to burning some BTC. I will look back into it, talk to the devs and see how we can make it work.
Now to answer some questions:
How long is the gameplay planned?
Will you add level/stories as time pass?
It's really too early to give you honest concrete answers on these two. We'll make it as long as possible but we definitely don't want to overstretch, either in time or resources. We'd rather have a fun short solid game, than a long drawn one with a dragging story. Regarding extra levels/parts, the story certainly allows for a second part about the aftermath, but we'll just have to wait and see how this one goes first.
Linux/Mac/Win game? android game? pure web based only? (offline & MMO mode? =D
Windows, Mac and Linux (on wine, but runs fine). Android is a possibility but we're rather worried about how it matches with our graphic styles, we're using spacey scenarios with unusual perspectives that might be complicated for small screen real estate.
It is a classical graphic adventure, so fully offline and no MMO.
Post-IPO, what are the possibilities to buy the game?
Price? over 10$ game on android is viewed as very expensive...
Price will be in the 10-15$ range, to be bought on the usual places: site, desura, steam (though it might take a little time to get in).We'll try to steer clear of the bundles during the first 6 or so months.
What about piracy?
(lock system with bitcoin key would be awesome, 'but global selling become harder as you have to sell BTC for newbie to buy the game with it)
This is not a problem we can actually solve, so we're not gonna really concern ourselves with it.

This is a really cool idea. I just bought my shares. Would it be possible for investors to get their names included in the game credits somewhere? =D
Definitely, I should have explicited this of course ! We also intend for in-game references to the past (our current) bitcoin culture and personas, so there's room for some in-game "appearances"...