I work at a small startup as a full stack developer. We previously used PHP to develop all of our applications and I told my boss we should eventually move to C# which he agreed. Over the coming months, I developed a fairly sizable C# framework on my own time outside of work (I was working on my own side project), including a nice ReactJS front-end with lots of components.
When a new project began at my work, we were in a huge time crunch. I had some fairly nice PHP frameworks I built at the company which would have made things go fairly quickly, but I thought it was time to make the hop to C#. To speed things up, I told my boss I would be willing to donate my C# / ReactJS code that I had been developing for a side project as long as its clear that I am not moving ownership of my code to the company. The company is free to use it however they want, but I cannot be blocked from continuing to use this code on my own side projects now or in the future. I didn't make him sign anything since he verbally agreed so I thought everything would be OK.
I currently have no suspicions that they plan to change their mind and prevent me from using this code in my side projects, but I'm a little bit nervous that I didn't make them sign a written agreement. If they find out I'm using this framework in my side-projects and am making money off of it, can they file a lawsuit against me? I have proof that I wrote the code myself on my own time by looking at GIT commit logs. The code was slowly committed over time in my own personal repository. By looking at the timestamps of the commits, I could easily show that I had developed and commited these files long before they appeared in any of the repositories at my company. Is this enough proof if my company decided to go back on our verbal agreement and claim that they own my code?