A couple of EA questions.

1) If you spend time developing a good EA, how do you keep it safe? ie. Can anyone see what EA's you are using and somehow download them (steal them)?

2) If you have a good EA, what is stopping you from running it on 100 PC's at the same time and making a killing? Or is running an EA on more than one PC redundant? ie. All trading can be done from 1 PC?

1) Hide it in plain site. There are good EAs with source code on this forum that few people ever look at, and there are other metatrader forums with more. If you can't make plenty of money trading and depend on a few dollars for some EA code that will probably stop working on the next wrinkle in the market you should get another profession.
2) The only thing stopping you is margin.

1. Keep it for yourself. Never publish it anywhere.
2. Nothing. My current EA is up to 3 accounts, the only thing I am running into is finding enough brokers who are willing to share their API since this EA doesn't run in MT4.