Yes, validation of open source code is a big problem. We would have no idea if the results returned to us were valid or not. So that's that's a factor for leaning toward closed source. We would like to have it so people can submit the code changes directly to us so we can validate there's no malicious activity going on. However, the BOINC framework doesn't currently support this. It's basically very decentralized and doesn't check with our server to see if you're running good binaries or not.

I do not wonder. It's the "magic" of optimization of code to speed. Try some and you will see yourself. If you do not want to try, just think about very simple case: different speed of different sorting algorithms.

There is no magic in computer sciences. The greater the difference in speed between two applications getting the same result, the more radical the differences between those applications generally are. This might make it a lot more difficult to check, and Travis has a point about holding off on the optimizations until the new code is out. However, I do hope they can work together in the future and help us all contribute as much as possible to science.

I do wonder how a computer (no matter how overclocked), can take 4 minutes to do a WU that I take 5 1/2 hours to do, that is extreme optisation I must say.

• Although I'm technically oriented, in BOINC world I've learned that distributed computing is a lot about psychology. So Travis may have preference to do a science work for MilkyWay, but somebody from project should think about the cheating, as in the crowd there will always be somebody thinking about cheating. And if there will be real cheating, other persons will discover it and the flame war will start. And there could be false accusation or at least controversy... None of this is good for project (from psychologic point of view).
  
• The optimization may be done for good motives. But optimizer may make unintentional mistake and the results will not be correct. Also, there could be some problem related to hardware - often there are unstable oveclocked machines used, which makes results incorrect. This also supports the opinion that quorum should be 2 instead of 1 and validator should eliminate incorrect results.
  
• IMHO the whole credit system is wrong concept (or unfair, depending on point of view). Look at the definition of cobblestone - it's about amount of time spent on reference computer, without taking into consideration how the time was actually spent. If the employer would pay me for time spent in office without any other conditions, without asking whether I do something meaningful or useless, I would sleep in the office everyday.
  
• Now the location of the source code is known. But now I do not want to do my own compilation, as at the moment it seems it would not help the project (see my 2nd remark above). I'll wait until project is ready for that... I hope the day will come soon.
  

obviously not hard enough as it's being "hidden" in plain sight ....
http://www.cs.rpi.edu/~deselt/

As has been posted many times. The source is open and available to everyone.