What wouldn't be the 5th time I've heard such stories, but I don't think it's in any way specific to IBM. Employers like that want any OT you do to be dedicated to THEIR endeavor, not somebody else's...even your own.
If you're able and willing to code in your off-time, you should be doing it for the good of the Company. /s
If you're able and willing to code in your off-time, you should be doing it for the good of the Company. /s