Very often, yes. The boilerplate IP contracts provided by most law firms usually claims one of: * All software development work you ever do while employed by the company. * All software development work you do using in any way any resource of the company, from computer to network connection. * All software development work you do related to the business of the company that employs you. * All software development work…
This also varies somewhat by state; there's a law in California (Labor Code section 2870[1]) that bars employers from claiming work that an employee does "on his or her own time without using the employer's equipment, supplies, facilities or trade secret information" unless the invention relates directly to the employer's business. I'd still check with a lawyer, though, even if in California --- and if elsewhere, mos…
Copyrightable works are not included, and so software isn't.
Reason for edit: Fixed typos.