The first, I wrote some software and signed away the rights to it for an insubstantial amount of money. This software vanished into the "defense" industry and was no longer mine to use for any purpose.
Second (it will take a few paragraphs to explain this) I've pretty much kept everything I've ever written on computers. Whenever I upgrade to a new computer I transfer all my old stuff to it.
My first computer was home-built using an 1802 processor. My next computers were Atari 800. I made some money with Atari 800 and Apple II stuff. Once upon a time I could write 6502 machine language neat, inline code, no assembler, usually embedded in BASIC, Action!, FORTH or some other abstract languages. At the same time I was gaining experience with BSD Unix. (I'm a University of California graduate. I first logged onto the internet in 1979.)
I first signed onto DU using a Windows 98SE computer. But I soon switched to Linux when I discovered Linux would run ALL my old software and open all my old files without much fuss.
I wrote my first and only novel using vi. No problem opening it in Linux.
On my Linux machines all my old computers are one click away. This is not from my current desktop, but similar:

I still own the actual computers, the ROMs, the floppies, the CDs, etc., therefore I figure the emulations are legal. But I've grown wary of starting the actual hardware because I've heard too many electrolytic capacitors popping like firecrackers.
I won't touch proprietary software any more unless someone is paying me and it's something I'm willing to abandon if the situation gets toxic.
All my DU stuff I consider Creative Commons with attribution.
