Competing products -- what's the law?

I had an idea for a web app about 3 years ago, but I haven't had time to build it. This year I've finally got some time and some interest/availability from a colleague, so we've decided to begin working on this idea (took forever, I know).

Sadly, in the time I slept on it, another company has built and released a product that has a very unique feature that's almost exactly the same as one I intended to build into my product. This feature is a key (you could almost say centerpiece) feature of their product, but I wasn't planning to make it as central to my product (i.e. it's not going to be the key marketing point, as it is for theirs).

Should I worry that they can sue me for some kind of copyright infringement? As I'm typing this, it seems pretty obvious that the answer is "no". But I'm not sure. Anyone know what laws I should look into about this? I'm not even sure of the correct terminology to search for on google.

You have three major things to worry about:

• Copyright
• Trademarks
• Patents

As far as copyrights, you can't copyright a user interface, (although Microsoft with their ribbons interface seems to think they can). See Lotus Development Corporation v. Borland International, Inc. http://bit.ly/9UwRf8 You definitely can't use any trademarks that belong to the other firm.

Finally, patents can be a major problem. It can take years before a patent is granted during which you could be infringing on it.

You might want to get some legal advice on how to proceed.