How not to lose the project?

Question

Copyright

There is a project that is being done outside of working hours and the problem is that I don't want to give it away for free.
I took on this project only because it has qualities that suit me:
A) I have an interest in the topic of its use
B) I may be able to commercialize it myself C
) If I get bored, then there is a chance to sell it to a company as part of a competition. Initially, it all started with a competition.
The company seemed to like the project. They wanted me to move the development inside the company. I am against this action, because. I have not received money for it yet, but let's provide the codes. My intuition tells me this is not going to end well. I will not receive money, I will lose intellectual rights.
If you think logically, then even entering into an agreement on supposedly "copyright is entirely with the developer" is complete nonsense. The name of the implementation is not difficult to do something similar.
What should be the agreement or what kind of licensing of the project to prevent an attempt to steal the implementation?
Or is it all useless and is it better not to sign anything at all? Just where the money - there is no honesty.

Answer 1

1. Take ownership of copyright and exclusive rights.
2. Then - license your product the way you want and sell them the right to use a copy under this license: sign a contract for the right to use.
Do not sign any contracts for the alienation or transfer of exclusive ownership of your work!