It depends on the definition of tenure... if tenure is defined as a closed interval (i.e. defined only for developers who've joined and then left) then it means that, of the developers who have departed, none had wanted to grow with the company, or the company had let them go. For a startup company this might not be a good sign.
If tenure is defined as the length of time the developer had worked, OR, has worked so far, then it means they have a core group of developers and aren't growing the development team particularly quickly. Again, this might not be a good sign for a startup.
It depends on the definition of tenure... if tenure is defined as a closed interval (i.e. defined only for developers who've joined and then left) then it means that, of the developers who have departed, none had wanted to grow with the company, or the company had let them go. For a startup company this might not be a good sign.
If tenure is defined as the length of time the developer had worked, OR, has worked so far, then it means they have a core group of developers and aren't growing the development team particularly quickly. Again, this might not be a good sign for a startup.