Copyright resides with the originator of the material. If it resides on your hard drive, it's yours. Non-exclusive rights means that Paradox could use your material, but they would have to approach you first. If you wish to proceed to publication on your own, and cite any Paradox game as source material, then you would likely have to talk to them for permission.
As T_H has alluded, it's a grey area, and an area that hasn't been properly addressed or challenged (and yes, we disagree about the "implied non-exclusive copyright" ramifications -- but that's what friends are for... ). There are a few legal websites that have existing case studies.
frogbeastegg: Most publishing houses will accept unsolicited material. If it's a novel, they usually request a query first. A query gives them a good idea of what you are proposing. If they are interested, they'll generally ask for the first three chapters of the novel and a synopsis of the balance of the proposed book. Most publishing houses have web-sites that list their submission guidelines. Not all publishers require agents. Hope that helps.
As T_H has alluded, it's a grey area, and an area that hasn't been properly addressed or challenged (and yes, we disagree about the "implied non-exclusive copyright" ramifications -- but that's what friends are for... ). There are a few legal websites that have existing case studies.
frogbeastegg: Most publishing houses will accept unsolicited material. If it's a novel, they usually request a query first. A query gives them a good idea of what you are proposing. If they are interested, they'll generally ask for the first three chapters of the novel and a synopsis of the balance of the proposed book. Most publishing houses have web-sites that list their submission guidelines. Not all publishers require agents. Hope that helps.