For me, the reason is simplicity, although I prefer public domain.

I think it depends on who your "target market" is. Non-viral licenses make sense if you want companies to use it.

I've never released my work under MIT or BSD. I release about half of my work into the public domain, about a quarter of it under a GPL variant, and a quarter of it remains under a more conventional commercial license.

If you want people to use it.

Companies are not that keen on GPL in any form.

I guess my question is why would you want companies to be able to use it for free? Why not release under a viral license with a commercial license also available?

Why is a large company using your MIT licensed code a good thing? Do you expect to eventually get paid for that work, or get recognition, or what?

> I guess my question is why would you want companies to be able to use it for free? Why not release under a viral license with a commercial license also available?

The amount of hassle it takes in most companies to licence software from a third party vendor is so immense that generally they will spend far more in $$$s to write it themselves instead.

Your average small hobby project or helper library isn't going to every make you any money that way, only something which is both very large/complex, and very desirable, would.

> Why is a large company using your MIT licensed code a good thing? Do you expect to eventually get paid for that work, or get recognition, or what?

It looks good on your CV and might get you a job there.

> The amount of hassle it takes in most companies to licence software from a third party vendor is so immense

Yes, for very large corporations. But smaller companies don't have such a large problem with this (and most companies are on the smaller side).