Answered on May 17th, 2013 at 8:20 AM
1. Copyright and patent rights protect different things and the knowledge you seek (about infringement) is obtained differently. in each case. 2. As for copyrights, if you haven't copied anything you will not infringe. If you do copy something, it gets a lot more complicated and you should consult an attorney. 3. Regarding copyright, you could be sued even if you haven't copied or done anything wrong. If this happens you should hire an attorney to help you- a skilled attorney should be able to help you win the dispute and may be able to recover your legal costs and damages. 4. Patents protect useful things and methods- in the US, the first party to file a patent application or publish a patentable idea may now obtain a patent that can exclude others from using that which is claimed. To have a very high level of confidence that no patent covers what you are doing, you need to find an an *expired* patent or publication, or other documented public knowledge showing exactly the same thing (e.g. that a patent covering the thing would be invalid). 5. If you don't have any of the above in hand, then you can search through patents and patent applications. This can be difficult and it is easy to miss things. For this reason, you should find a highly skilled technical patent attorney who has significant hands on experience with patent disputes/litigation to help. Nevertheless, at the end of the day, there is always a possibility that something was overlooked- the amount of uncertainty will depend on the skill and scope of the the search. 6. As to your second question: you could search for patent applications and patents in the names of company employees and/or assigned to the company- but this assumes that the idea is protected by patents rather than a copyright or trademark. Besides searching, you could always ask them ;-)).... but doing that has its own drawbacks and/or risks. 7. "Similarity" that you reference can boil down to a legal question... the criteria, and what is protected, are different when it comes to copyright vs. patent protection, and legal knowledge, technical understanding, and experience are generally necessary to tease these things apart. 8. You can find a number of books with titles such as "