A general rule I use. Do not protect the master code in anyway, it is better to protect the PC. If you need to share the code in a password protected way, use a source distribution and apply the passwords on the COPY. If you are really woried I simply would not distribute source, just send exe to the client this way you have removed the code and no source protection is necessary.
I would be interested in other methods. Most code I develope is so specific that there is little reason to steal the source, that is without the hardware many labview applications are just not that relavient. I have had a few clients that were very concerned about the security of the original code, and here I can make exceptions, but it is rare.
