Open Source application GPL legality

[shd]

Hello,
I'm Open Source initiative fan who's willing to manufacture MMORPG 
computer game and share it's precious content with the humanity :). 
Because of scarcity about repeated closing my application by 
money-for-nothing+crap guys, one of GPL tree would be the best choose. 
Blocking possibility thing is really important thing for me, without it 
- I wouldn't share sources to mass-market. Keeping in mind quality of 
gaming experience I encountered problem with player protection. More 
specifically, absolutely opening application (in this case client) means 
allowing to build automated cheating utilities (such as computer bots 
and other 'hacks') which would completely ruin fun for others. After 
considering many ideas of restricting 'hack-programs' use... After 
exclusion of poor video stream transmission (: I acknowledged it as 
impossible.
To save possibility of making this kind of application open-sourced I 
digested method which is making use of raw client data hashed with 
server delivered seed as authentication token which can be used to 
verify (surely open sourced) client integrity. Thanks to this idea we 
can make client and server in Free Software way simultaneously not 
breaking functionality (delivering fun in RPG way) and letting to 
everyone open-up his own game realm. As someone of you probably spotted, 
key of the whole concept is having concrete entity of client (binary 
data) unknown for 'bad guys' whose aim is to destroy game balance = fun 
= use of application.
The question is - can I share my application released on GPL license at 
the same time dynamically obfuscating and morphing an executable file 
with *not shared* utility? Result would be - client + server are both 
open source, but if someone wants to stay connected with *my* server he 
has to use concrete (my) compilation from.

Cheers,
Mariusz Gliwiński