You can use GMF to create a so-called RCP application (rich client platform), as described in part 4 of the GMF Tutorial. The resulting editor will be much smaller and more light-weight than a full eclipse, but also quite limited; e.g. I found it impossible to add additional (custom) views other than the editor window, properties and outline view.
Note: I have not used this myself (just tinkered a bit) and I am not sure, how mature this is.