Well, the black outline is part of your image. I cannot help you there. However, seeing this problem (as all mine have had no text so I didn't notice) I will look into 'flipping' the texture on export. The new version also helps with several other issues, including deleting existing .bin files and gives you a icon when selecting your decal. I'll see if it is possible to flip the image. Once that is done version 4.1 will be released.
Also, I am *thinking* version 5 (not 4.1) will include animated decals. They'll have many more options than a normal decal, as it can be flat on the ground, rotate with the player, or stand without rotateing ect ect. I'll also have to make it support the animation in the program so you can preview it. Well, that is all just thought now, I'll go see if I can get the flip to work.
EDIT: if any parts of the documents are pure black (RGB(0,0,0)) then they will come out transparent.