However the most obvious countermeasure for such a ban would be greatly extending the vesting periods of stock options... )
I fail to see the negative here. If you choose to leave, you have to leave with unvested stock options, and that is your choice. With a non compete clause, you cannot legally take a particular job, no matter how good it seems. It's illegal, and not a choice at all. Countermeasures only happen when you don't ban something, but rather, kinda, sorta, maybe change it in a limited but not sincere sort of way. You proposed example is not a countermeasure at all, but rather, a reasonable suggestion.
FREE SOFTWARE: is software that you can legally run without paying someone. It might have been written by some guy just proving he could do it, it might be the Linux kernel, it might be a utility from a commercial software firm that they've licensed for free use. It's free. The author(s) might or might not show you the source code and tell you how it works. The authors may or may not have copyrighted the code. The fact that they're not charging to use the software makes it free. If they don't want to share their code, they don't have to.
This is a common misconception. Free software refers to freedom, not price. If it is Free software (not free software), and you distribute it, you can charge all you want, but you MUST be willing to distribute the source code. Free software is a subset of Open Source Software. F
The next person to mention spaghetti stacks to me is going to have his head knocked off. -- Bill Conrad