I'm currently doing free lance work for what is basically my former employer. We have no official contract signed or anything. When I left my former job we separated on good terms and I agreed verbally to help them out with freelance work if they needed it.
Now the problem is that this current project has dragged on for months when in the beginning they said it will only take a few weeks. The delays are not because of me. All of the work I was suppose to do is done already but now they want me to continue doing other stuff that is not my responsibility. My question is how do I tell them that I no longer have the time to work with them because of my current job (I'm a co-creator of a start up company). Is it ethical on my part leaving the project in its final stages if my part in it is done?