I've read the recently answered question: H1B opens a business in the USA
http://answers.google.com/answers/threadview?id=731971

My concerns are slightly different and I would like to know if the
following operations are legal and feasible:
1. My sole proprietorship will be always zero revenue.
2. As the owner of my business, I myself purchase assets and claim
expenses under my business. (Will I be considered an "active role" in
my business, and therefore violet my visa status?)
3. Assumed 2. is legal and feasible, I use a business credit card to
pay the bills of my business and access the benefit of my business
card.
4. Will I save total taxes by running such a sole proprietorship? How?

I would like to do something after work for fun such as a free web
tool, a free script, or a freeware. I don't intend to make any profit
from it but I want to make my recreation less expensive or help save
some money.

And last quick question: Is it correct that I don't have to file any
document (in CA, USA) to start a sole proprietorship doing business
proposed above (writing some free tools/freewares)?

Just a free comment, and obviously no legal or professional advice
(see the disclaimer below).

It would seem that if you own and operate a sole proprietorship, by
definition you would have "an active role", regardless of whether it
makes money or not.
I think it would be difficult or impossible to get a credit card for
the business if it is not registered.