Forth immediately comes to mind with those constraints. 8K is an order of magnitude less storage than what the IBM 704 that lisp was first implemented on around 1960 had.
I think programmers (especially these days) over estimate how much advantage they get from reusing other packages. Because it becomes so much more difficult to refactor your code when you can't change some interfaces, you may end up with more (or at least more complicated) code than if you wrote something that is tailor made. In languages where you have a lot of facilities available, it is one of the hardest decisions to get right. When you are forced to write everything yourself, then it's easier to get the choice right ;-)