MF> [1]Is there any record anywhere of the reason(s) why these proposals MF> were rejected?
In some FRLs you find the reasons, but not in FSCs.
MF> [2]Is a software developer permitted to implement any of these MF> rejected proposals in his/her software?
If you want to write a tosser, you have too implement some proposal that hasn't made it to a standard (like FSC-0039). You can implement whatever proposals you like, but most are just proposals and are rarely supported by any software.
Do we have a list of FSCs that are relevant?
MF> [3]Am I correct in assuming that the FSP's are proposals awaiting MF> either acceptance or rejection by the FTSC?
The FTSC is practically dead, nothing will be accepted or rejected anymore.
