If you are hired to create a piece of software X, then it is a work for hire and your employer holds the copyright. If you are hired to write software X and also write software Y on your own, you hold the copyright. However, you could well get fired for using company resources for personal projects, whether it is a pen, computer or software license. If your contract actually says e.g. "If you use any company resources in a personal business venture then we hold all rights to that venture an an extension of your employment", you might have a harder time maintaining that this wasn't a work for hire, but that would have to be sorted out in court. But if they just said "Don't use our stuff", then it would be a breach of contract. The point is, ownership of the created work is not determined by ownership of one or more tools used to create the work. You could ask for exceptional permission to use their license for your product, or you could buy a license and then sell it to the company, or you could ask them to but a separate license for you, or you could buy it yourself and then ask them to reimburse you. Whichever way you do it, you would own the copyright, unless of course they made it a condition of purchasing / using / reimbursing that any resulting IP be transferred to them.