Are you a grad student? Even if you coded it, and even if you believe it to be "your" work, you probably can't claim complete ownership, since there was likely some input from your advisor and perhaps other people in the group.

My students regularly write code, but my input is almost certainly present in the choice of problem, and usually in algorithm choice, design, debugging and verification. But the student would write close to 100% of the code.

In practice, very few codes written for academic purposes can be commercially exploited -- is this a money issue, or a "moral" issue??

In my group (in physics/cosmology), we don't necessarily release our codes, since they can often be used for more than one project, and we want to harvest the full fruits of our labor (and they are likely only of use to other academic scientists in any case). However, I would not share or reuse a code a student or post-doc of mine had worked on without discussing it with the person concerned, and I would expect my students to pay me the same courtesy once they move on (and so far they have).

My advice is to talk to your advisor and don't be an ass. Unless there really is money involved it is likely that no-one is trying to screw you. If the issue is academic credit, you should simply make sure that the project itself is described in a paper which will be cited by other users. And, if you can, release the source, with a good README since the academic world ran on "reputation" long before eBay was invented, and writing a widely used tool will do you no end of good.