Dear mimi,
You have three main concerns:
1. non-compete agreements: If you did not sign any non-compete agreements, then you are able to freely compete in the market place.
2. Non-disclosure. Non-disclosure is a little trickier. Even though you may not have signed any non-disclosure agreements, you had a client relationship, which must be honored. You cannot get by with, in the course of your work, disclosing your former clients trade secrets or anyother proprietary information which can include: processes, procedures, intellectual knowledge, financial status, business plan information, etc.
3. Infringements: You have to be concerened with theft and use of intellectual knowlege which includes: patent infringements, copyright infringements, and trademarke infringments.
You can check to see if the company or any of the ownership and officers has patents, trademarks or copyrights related to and incorporated into your product. If so, you hve to get their permission to use them or they may have a right to sue for infringment, damages, and roylaties.
Use these links to conduct your search:
http://www.uspto.gov/ (trade marks and patents)
http://www.copyright.gov/
YOUR PAYMENT AND BONUS IF ANY MAY BE TAX DEDUCTIBLE
Edward M. Johnson