Not currently, no. It doesn't help that the game is tied to 640x480 internally.
The easiest solution would be to render the game to an offscreen texture first, and then upscale that to the monitor resolution.
Well, there is some experimental code in there that takes a vaguely different approach:
Set the screen resolution to 1280x960 (For a clean 2x upscale), and keep track of the scale-factor, so that the coordinate system internally still sticks with 640x480. This does give you a (if i remember correctly) linear upscale (might be GL_NEAREST if I'm wrong though) of 2D-elements, and allows the 3D models to be rendered at a higher resolution. Which is a tad better than resizing the offscreen-texture, even though the textures are still the same, as there is less room for aliasing.
Currently this is experimental, and NOT implemented (nor will it ever be) for the software renderer, due to how slow this would be there.
Since it's experimental, and not thorougly tested, it's thus not user-available (and I can't even guarantee that it ever will be). I do however see the need for SOME such solution down the line, so that we can supply a resolution that the screen can be in semi-natively (allowing the rest of the problem to be solved by screen-scaling).
Down the line, I'd probably want to look into supplying a solution that allows us to deliver a native wide-screen-resolution (with the obvious black-bars on the sides), to allow modern screens to work in native resolutions.
The software renderer will be forever stuck in 640x480 territory though, and I can't give any promises about the GL-renderer. (I'd be interested in knowing about any issues with regards to the in-progress GLES-renderer though).