CharPad and SpritePad are both "portable" apps and so require no installation but this also means their project files are not automatically associated with any particular executable(s).
I'm sure it's possible to make an association manually which I'm guessing is what you have done.
That's fine but one problem with doing that is that when a new version is released you will likely have to make the association between the file type and the (new) executable again.
Personally I never bother associating files with portable apps but I will look into the issue for the benefit of those people that do.
Thanks for bringing this to my attention.