Asker, I agree with Attorney Ballard.
It sounds as if you are a co-author and as such cannot stop the other co-authors from selling or exploiting the software, and you should be careful about calling them cheaters, etc. It is unclear to me from your statement of facts whether the other co-authors sold a software license to X, or actually sold their rights in the underlying software to X. If they sold a license, they owe you your pro rata share of the sale (i.e., if there were 4 co-authors and no other agreement between you, you are owed 25% of the proceeds from the sale of the license). On the other hand, if they sold out their entire interests in the software, then you and X are now co-owners of the software -- with you having the same share of ownership you had prior to the sale. For more on co-authorships see: http://artlawteam.com/two-heads-better-the-legal-side-of-collaboration/
In any event, you need to speak with an IP attorney who can help you to assert your rights based on the actual facts and circumstances. Good luck to you!
Asker, Attorney Ballard give you solid advice as regards the copyright issue. There is also a possible trade secrecy issue that may be in your favor here, and may even show the "theft" of which you speak, depending on the facts. Be sure to get to an intellectual property lawyer who deals with trade secret law issues, as well. For your software related issue, I would recommend Aaron Hendleman of Wilson, Sonsini in Palo Alto. He was formerly IP counsel for Apple and before that a clerk for the 9th Circuit Ct. of Appeals. He can get you the most you can get. Realize that may, as Attorney Ballard suggests, just be your pro-rata share of revenue of the others, but if there is theft of trade secrets, you may obtain substantially more.
its not a license, they sold the entire product and got money and cheated me by not paying anything for my work. x knows that i was not paid and entered into the deal to take advantage of it.
If they purported to transfer a 100% ownership interest in the software to X, X may not have received what X bargained for, and it is likely X has a claim against the other co-authors for a breach of their representations and warranties. I would argue that you continue to own your % interest, and have a claim to that % of any amount that X makes (unless X wants to buy you out). But, as all of us have indicated, you need to meet with an experienced IP attorney in your area and go through all of the relevant facts and circumstances in the privacy of an attorney-client meeting. I would second Attorney Burdick's recommendation of the Wilson, Sonsini firm (if they do not have a conflict). Again, good luck to you.
in that case whom i should sue? x or others or both? given the fact x knows that others cheated me before he bought it.