I read last week that Microsoft will turn over the Windows source code (some 30 million lines) to a few governments so they can examine it for security reasons. They're doing this in large part because of Linux. Anyone can get the source code for Linux, so examining it for security holes is far easier than a closed source OS like Windows. Linux is a good OS and is gaining popularity, especially at the expense of Windows market share.

As for possibly having their code ripped off, it has been going on for a long time. Some countries, most noteably China, are known in the software industry as "one copy" nations. They buy one copy of a piece of software then blatantly pirate it. They can easily do that without having the source code.