Your question relates to shareholder rights. Specifically, you're looking for solutions which distribute/protect rewards, rights and powers
In other words, you want to make sure that you are rewarded fairly and that you enjoy some sort of decision making power/leverage in your company
The solutions to these problems include legal documents like vesting schedules, employment contracts, stock purchase agreements AND certain interpersonal skills.
If you want to retain a role in this company and require answers, you need to
a) post your questions on
http://www.startupjunkies.org/forums/index.php and
b) see a lawyer
c) develop your interpersonal skills
Overall, I very much doubt that you have a future working with these guys. You are not assertive enough to have worked out all these issues for your self, and therefore you've naturally lost trust in these people because you have failed to communicate, and protect your rights. It's not their fault. It's your fault.
Any consequent actions involve you screwing your partners (i.e. competing against them, hijacking the source code etc..) and I'm not able to advise you in relation to that.
Cumulatively, on a purely objective basis, and I'm sure you're a nice guy - it's more likely than not that you are not ready to strike out on your own and take leadership of your own startup. If you were, this thread would not have happened. All of the issues you've raised would have been resolved - but they weren't.
I advise you to continue in your role as a technologist, take a salary, continue working with these people and learn as much as you can about sales and management. If you strike out on your own, based on the information provided and inferred - you may end up in a worse place than you are now.
Finally: Your statement "developing some software for an investor" is incorrect. An investor is a person who buys securities from an investee. You have not sold your investor any securities, therefore, you are not an investee but a "partner" or a "contractor".
If you are a "partner", you have claim to a share of the "partnership assets". If you want to leave the startup, you can offer to sell these partnership assets to your partner, or withdraw them from the partnership and leave your partner hanging.
Alternatively, if you're a "contractor", who developed software for your offeror, you can claim a payment. This can fall through if the offeror asserts that they've already provided you some sort of a consideration (i.e. work experience). Furthermore, the offeror can claim that there is no contract for lack of certainty, in which case - you have no recourse, other than equitable remedies.
The point: Have a clear understanding of your legal position because it relates to your rights. Don't misuse words which have special meaning (i.e. "investor").