Omni Magazine ran from 1978 to 1995. I still have somewhere the junk mail that I received asking me to subscribe in 1978. I kept it because it included a very nice print of a spaceship skimming over a planet with lush vegetation. I thought that I would frame it. I have no idea where it is, but I know that I didn’t throw it out. I was just starting to write stories again when Omni went out of business. I would have submitted to them if they had stayed open for another year or so.
Someone has scanned and uploaded to the entire magazine run to the Internet Archives. I wonder how they were able to to this because it is obviously covered by copyright laws. All that I can think of is the title was lost when the magazine went out of business and disappeared without anyone buying up the serial rights. The individual rights might have reverted back to the authors and there are many impressive authors in this run. Gibson or Martin would not have allowed their stories to appear anywhere for free, so I don’t anticipate this staying up for long.
Normally a writer sells first serial rights to a magazine. It is rare when a magazine buys all rights or even first and second rights. No writer would sell all rights unless the money was huge. This would mean that the individual authors have the rights to their stories.
I would, if I were you, spend a few hours and download these magazines. You can read Martin’s Sand Castles, which is very good, or Gibson’s Burning Chrome and Johnny Mnemonic as they first appeared.
If you have a tablet or iPad, download the PDF version as they work really well on table screens. There is a Kindle version, but my experience is that the Internet Archives mangle the books when they convert to Kindle format. There is the ePub format for those with other eReaders. If you have a smart phone you can get a free eReader app so that you can control the font size at least, but it may be hard to read without your granny glasses.
Get them quick before they are taken down.