Here?s an idea. The following is very simple, perhaps it might work. You burn the files on a CD and mail the CD to yourself. When you receive the envelope, don?t open it, just put it aside. If needed, the date on the envelope would prove what you need to prove.
That?s very old trick (or ?trick?) I red in Sinclair User (British 1980s magazine for Zx81/Spectrum users). Back than, programmers were mailing the tapes with the games they coded to the software companies. This was an inexpensive method to protect themselves of rip-off companies.
I guess closed envelope with your CD is stronger proof than a page at archive.org.
