The issue is that coders can only load so much code into their brain at once. There's a huge switching cost involved in going from 'own-app' to 'company-app'. You are simply not as productive when working 2 significant projects at the same time.

This simply isn't true, in fact for many the working on only one project is extremely boring and the home project may actually revitalize his interest and let him pursue more interesting work that further increases his skills. That increase in skills will benefit his other work projects.

you're also not as productive if you play video games all night, or if you go drinking, or if you ...

Not to mention things like having children or relationships.

Excellent point, I’m probably the only hacker I know who do not play video games; for some reason I stopped when I got in college. But I remember as a teen I drained me as much as studying, I think playing video games can be harder (or equal) on your hacking resources as actual hacking.

> I’m probably the only hacker I know who do not play video games;

Emacs + code is my video game:-) I think there are quite a few of us, actually.

Yip, I am another one. The only think my xbox (not a 360) gets used for is watching DIVX's on!

M-x tetris!

Quality - I didn't know about that!

Games, drinks, children, etc. are diversions from the activities of software development and business which the employer is paying you to engage in on their behalf.

Participating in them outside of office hours would tend to _increase_ your productivity at work by giving your head a rest.

mmm... nope.

Our most productive employees are the ones without kids, families or bustling social lives. And those same employees are the ones who are working on "side" projects while they are also working for us.

Any company that would tell an employee that they can't work on a side project, either as a business or a hobby that is not in direct competition with that company is setting itself up for failure because it's a sign of a larger cultural issue within the company itself, stemming from severe mismanagement.

"Side projects" and open-source projects are great for self-education. I've nothing but good things to say about them for employee improvement.

Running a separate business is a different story altogether. Do you really have productive employees who are operating software development companies on the side? If you do, I can guarantee their primary attention does not lie with you (even though their primary income is being paid by you).

This, I think, is the key distinction. Running a business is a whole lot of work, and much of that work does not make your guy a better software developer. Running a side business is probably going to diminish a programmers productivity.

Writing an application (and ignoring the business and customer service side of things) likely will make your programmer more productive, 'cause he learns all this new stuff.

I take it you've never had a baby around the house? Or broken up with a girlfriend? Those things have affected me way more than any coding ever did.

Children give your head a rest??? Either you have eerily well behaved children, or you do not have any children.

Yes, but that's not something a company owner can control. If the employee is building, say, a website in his own time he is at the very least giving the owner the illusion that it is something he can control; in the end it all depends on the IP clause in the contract. For both employer and owner it is better to take on a "Don't know, doesn't hurt" attitude.

I feel that if an employer pays me for 8 hours, I owe him 8 hours - not my whole life and soul.

I find my day job productivity and side project productivity rise and fall in concert. Rarely does one work against the other.

This is not true across the board. It's very sensitive to people, projects, levels of interest, and time between switches. For me, it's especially false with boring projects, where I simply have to be able to switch to something interesting.