I'd want to know your experience and know-how about the legality or not of:

I have the next question grid :

Fully Free software LPGL Software Nonfree software
Read ascii
Read ascii that has
some coding

write ascii
write scii that has
some coding

Read ascii
Read ascii that has
some coding

write binary
write binary that has
some coding

1. In the case of ascii coding we can assume that is easy to discover.
2. In the case of binary coding, we can assume that some inverse engineering is needed to know how is the structure of the file and the meaning of codes..
3. We can assume we are doing import - export utilities.
4. What can be happen if we are writing into an existing file created by the original soft.?

Thanks