Suppose I signed an agreement during employment that everything developed during my term of employment will be owned by the employer (or something alone those lines...)

Say before employment, I developed an awesome software library for personal use.

Is there any risk (say of losing ownership of this library) of using this software library in the company's product?

What if said software library was developed during employment but in my leisure?

  • If you incorporate it into the company's product without any licensing you will effectively have given it to them for free. You can sell it to them, saying, "here's something I wrote before I started working for you," and then negotiate a price.
    – phoog
    Jun 9, 2016 at 4:05
  • If I do incorporate it into the company's product without any licensing, can the company sue me if I later use that library in another product in another company? (i.e. will the company become the owner of my library because I incorporated it into their product?)
    – Rufus
    Jun 9, 2016 at 4:26
  • In theory, no, they won't come to own it. But there could be a dispute about the facts, and it might look like you stole it from them. That's why you should negotiate with them before incorporating it; even if you don't want money, you could grant them a license that allows you to continue using it. If you're serious about this, talk to a lawyer.
    – phoog
    Jun 9, 2016 at 4:30

1 Answer 1


You run the risk of ending up in a dispute about priority: that is, "You say you did this before your employment, OK, prove it in court, meanwhile we will keep using it thanks". Remember, common law legal systems adopt the premise that the onus of proving something rests with the person asserting the entitlement: you in this case.

So, don't have the dispute when there is something at stake, have it before your employment commences: "I have a software library that I have developed here on this CD-R. I am willing to licence it to you so I can use it as part of my employment on these terms: blah, blah, blah."

  • This is very common practice when entering into an employment contract or NDA in which you might have existing IP: The agreement will typically provide for an addendum on which you are supposed to list everything that you claim as your IP before signing the agreement so that questions like this can be more easily resolved.
    – feetwet
    Jun 9, 2016 at 16:04

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