First of all, what you have is a provisional patent **application**. For now, the provisional patent application is not publicly available. This can be a big advantage to you. You can use this time to improve your invention and file additional provisional applications. If you don't plan on making/practicing the invention yourself, you should make sure to try to think of everything possible regarding how that invention can be improved. This would (hopefully) come naturally to a practicing inventor.

When you file your non-provisional application, your disclosure will be made public ("published") 18 months from the filing of the non-provisional.

While your applications are not publicly available, I suggest waiting until you file your non-provisional application(s) to talk to others. Quite often, provisional applications do not have the detail or the scope that the non-provisional will have -- due to the time spent on getting drawings accurate and making sure everything is included in your non-provisional applications. It is best to have a complete application before talking to practicing companies. Sophisticated companies will take advantage of information not disclosed in your provisional application to file their own patent applications.

If your applications are not publicly available (or even they are published), you should sign confidentiality agreements (non-disclosure agreements) with anyone you talk to about licensing or buying your invention. Keeping track of who you talked to with confidentiality agreements can be the basis for "notice" of the invention by an infringer -- when they eventually steal your invention.

You can sell your idea anytime, but a provisional application is worth a lot less than a non-provisional application which is worth less than an allowed application or issued patent. Provisional applications are generally not as complete as they could be -- and require additional time and finesse to complete the non-provisional application. In terms of appearances, if you are not willing to put in the money to file the non-provisional application, the invention is likely not worth that much money.

Companies as well as non-practicing entities may look at provisional applications, but not for long, and will not give you the kind of money that you may get from selling a fully examined patent. Of course, it depends on how good your invention is.

I am a patent attorney generally on the patent owner's side.

Signing such a clause should make you nervous. You don't want to be responsible for the major company's infringement. The major company is likely getting more benefit out of using your software than your company is making by selling licenses.

The previous gentleman's answer is incorrect. Anyone can be sued for patent infringement if they make, sell, or *use* the claimed invention. It depends on the claims in the asserted patent. Based on experience, it's much more likely that the larger entity would be sued for infringement.

A patent infringement case could cost anywhere between $350k-$5M+ USD.
http://www.cnet.com/news/how-much-is-that-patent-lawsuit-going-to-cost-you/

In order to properly answer your question, I would need to know why you feel it's "very unlikely" that someone would sue the major company for using your software.

If the major company won't back down on this provision, the best thing you can do is determine if you need IP (defense) insurance. If a patent attorney determines that it is necessary, raise the price of your license and get IP insurance.

Yes. Put everything in one provisional, if you can. But the provisional is worthless unless you file a non-provisional within a year of filing the provisional. Make sure to put as much detail about 'structure' as you can (computers/servers, memory, hard drives, processors). Because you likely will be filing business method claims later on, the structure will be necessary to the claims.