Amazing Computing has been out of print for so long (approx. 16 years) that I don't think the parent publishing company (PiM Publishing of Boston, Mass) is even in business anymore. You can try to contact them directly but as they're out of business, good luck with that. I'd go ahead and post the material and since you aren't charging for it, the now defunct company or publisher can't claim that you're profiting from their work, I wouldn't worry about it. But if they do contact you and request that you take down the material, then you should obviously oblige them. I've seen most of Amazing Computing's magazines scanned and shared in PDF form on various sites and no one has had a problem with it. For example, they're available here for free:
https://archive.org/details/amazing-computing-magazine-1998-02
