van Riebeeck said:
It also really makes the interaction between a RT and the Adeptus Mechanicus very interesting. To take but a small example, if I am right one of the conditions under which the Ad Mech and the Imperium got bound in this tightly locked alliance was the complete and full right of the Ad Mech on any STC's discovered. As semi-independant actors with an Imperial writ, how does this apply to Rogue Traders? Do they have to hand that precious STC over under the Iron rule of Law (backed up with the fact that to keep their ship working they simply need the Ad Mech, not to mention the fact that the Ad Mech has some of the best ships availiable to humanity to back its threats up) or can they negotiate about its price and reward. And to complicate matters, in good old Imperial tradition, the Adeptus Mechanicus won't be a smooth centrally controlled body, and each forge world will vie for such a juicy price.
FvR
A better question would be, why would you even try to keep the STC to yourself?
A Rogue Trader isn't in a better position to exploit the knowledge than the AdMech, noone they could sell it to is either (unless you could the Dark Mechanicus, and if you're going to truck with traitors and heretics, then you might as well throw all the rules out the nearest airlock).
And it's not as if the Adeptus Mechanicus is going to ****** it away without even a thanks, on the contrary I think you'd be richly rewarded for such a find, assuming the find wasn't something dark and forbidden (like AI).