I am producing this project in the belief that Cosmos is now in the public domain.  This is based on four things that I understand to be true:

1. Per the Copyright Act of 1909, when the work was published in 1933, an explicit copyright notice was required for the content to be protected.
2. For works published with notices at that time, the copyright had to be explicitly renewed for protection during or immediately after the 28th year following its initial publication.  If renewed, the copyright was extended for an additional 28 years.
3. My inspection of my copies of Science Fiction Digest, Fantasy Magazine and the Cosmos inserts shows that early issues carried no copyright notice.  The first copyright notice seems to have appeared in the September, 1934 issue of Fantasy Magazine.
4. It seems unlikely that the copyright was renewed on the Cosmos chapters published from September 1934 onward.  This renewal would have had to occur in 1962.  If the rights were renewed, the 28-year extension would have expired no later than 1990.

I referred to this page for information on relevant copyright rules.

If the rights are held by anyone, I believe it would be the estate of Forrest J Ackerman.  He republished Cosmos in the Ace editions of the Perry Rhodan series of books beginning in 1973.  I tried to speak with Forry shortly before he passed, and I’ve since attempted to contact his representatives without response.  If anyone is aware of existing copyright holders to this material, please let me know.  It’s not my intent to profit from this endeavor, so hopefully an appropriate arrangement could be made.