I dont know how much actual help this is going to be, but:
Dont p*ss your programmers off. Dont get them in a position where they WANT to give the source to a competator. Most places undervalue their developers. given where you are (SO), I guess you are less likely to. Nothing got to me more than seeing the sales folks out for games of golf - paid, and paid for, by the company - while we had to fight to get pizza once a month.
Really, if your direct competitors got your code TODAY, what would it do? Is your product or vertical market that stagnant that you wouldn't release newer, better versions before they could react? Is there no room for innovation? Most companies overvalue their "proprietary algorithms and in-house developed knowledge". Sure, it may cut some time off, but it's only about 10% of the problem.
If you got all the source for all your competitors products, how much actual use would it be? I'd guess it would set you back months. Not forward. Back.
If you had a clean system, and little external/internal knowledge, how long would it take you to get your own product into a buildable state? How long would it take to drill down into the code and workout what is going on? How much time and money would you waste trying to work something out, rather than spending time and money on how to make YOUR product work better?
I've actually been in the position of having all the source - 1million lines+ of code - to a competitors product. We did nothing with it - aside from and a bit of a poke around and then delete it, which was more than I was comfortable with - but I would expect that we'd have chewed up months of time just to get to where they were then.
So we nuked it, slapped the id10t who got it (yes, a developer/PM who came over from the other company), and thought about how to make OUR product kick so much butt that it didn't matter what they did.
Much better use of time. Worked well, too. We had differentiators, not just re-hashing the same features in the same way they did them.
Sorry, but there is NO way you can stop people getting stuff out, and still be able to actually work. You can stop them WANTING to do it, or make it so there is no value to them having it.
We were worried about people decompliling our code too. We stopped worrying when we realised that WE had enough trouble working out what was going on inside 500K+ lines of C#, C++ and HTML code talking to MAPI/Exchange. If someone can decompile it and work it out, then we want to hire them......
BTW, for clarity, and given who I NOW work for, I should point out this is NOT my current employer. This was quite a while ago.