[Preface: This focuses solely on the legal situation at the magazine buyers side, as any contract between author and publisher will not only include the right to produce multiple copies - that is the printed magazines - but more important be of no difference than with any other publication contract. At least for the part of the printed article/listing. Additional products (disks, boxes, etc) leave the scope of this question.]
Today we live in a world ...
"Today" might be the most important part here, as today's situation has not always been that way or naturally given.
Let's dive into legal history:
Way into the 1970 software (source and code) was not seen as a fixed, tangible product. Code was viewed as a utilitarian good, not creative work; source equalled to mathematic formulae which are as well not considered protected by any kind of copyright law.
This only changed slowly during the 80s as more an more companies argued otherwise. In the US the turning point can be seen in the early 1980s, first in 1980 by a change in copyright law and second in 1983 by Apple winning against Franklin in a 1983 court case.
US copyright law (17 USC) acknowledges a computer program (*1) as a subject of those regulations but also added §117 implementing rights by allowing owners of a copy to make further copies - including copying a program into a computer for execution (*2). This is a special addition to the general doctrine of first sale in §109, restricting rights to the point of sale (*3,*4).
In 1983 Apple sued Franklin for using the Monitor ROM code with their clones and won, marking the point where code was considered copyrighted even in binary form (*5) and without carrying any explicit copyright note (*6).
Other countries enacted similar regulations during the 1980s and 90s, cumulating in the 1996 WIPO Copyright Treaty, resulting in today's almost universal acceptance of programs as subject to copyright regulations.
[...] 'type-in' style programs that were published in various magazines back in the 1970's and 1980's.
Who doesn't - also, some magazines still do so although in way reduced amount compared to that back then.
Although these programs published their source code publicly, it seems clear these programs were not in the public domain nor were they open source (as we would define it).
You mean as some define it today?
My best guess is the rights to the program were retained by the author and the magazine acquired the publishing rights.
Further, I would guess the magazine reader probably had (unknowingly) purchased a license for personal use when they bought the magazine (always read the EULA!).
This sounds like a misconception, as a licencing is not at work here. Also we need to consider that it's all dependant on time and place. As shown, with the US example, before 1980 software wasn't considered a protectable piece of work, thus also nothing that could be licenced as well. In fact, all the EULA bloat that hit us later on is a result of that.
So before 1980 there was no need for buyers of such magazines to think about this at all. After 1980 the situation was clear in a way that as well noone had to think about. This becomes obvious when considering that
- the program as a piece of work,
- the work being printed in that magazine,
- the magazine being rightful obtained,
then it's clear that
- the owner may copy that program (aka type in)
- the owner may run that copy
- the owner may save a further (permanent) copy of that
- the owner may again load (copy) it again into his computer, repeating the cycle
All of that is without any question legal as long as that person continues to own that magazine.
And where does that leave the legal status for these types of programs today?
As mentioned a non-issue as long as one also owns a legally acquired copy of the specific magazine holding the program source/code. This of course includes versions in other media legally obtained ,no matter if that media was sold back then with or without that magazine copy, or was some later compilation disk or CD holding a binary copy, a text file or a PDF with the source text. It's all about continued ownership of the original media. (*4)
Otherwise it may not be legal to own a copy of that program. No matter if nowadays typed in from a scan at archive.org or on a (non genuine) floppy bought at a car boot sale.
Then again: Nullo actore nullus iudex (*7).
Did magazines publish the equivilent of an end user license in the fine print?
Some added fine print about their listings, but usually to clarify. Also, any restrictive 'Licence' would be void, as a licence must be agreed upon before usage(*8). So far I can't really remember any shrink-wrapped magazine (*9) with some licence tacked on :))
*1 - Using a definition vague enough to cover source as well as code:
"A 'computer program' is a set of statements or instructions to be used directly or indirectly in a computer in order to bring about a certain result."
*2 - In fact, it's that 'copying' of a program into main memory that was used as a main argument to make copyright law aplicable.
*3 - This is also the base for resales of software,including unbundled or otherwise discounted copies which the original manufacturer did not intend for resale.
*4 - In many ways later EULA legaleese was invented to restrict a user's rights again - possibly legal in the US, not really in many other countries.
*5 - The decision was also the reason why IBM could squeeze early clone manufacturer and force later ones to buy clean room BIOSes.
*6 - In fact, until that point source distribution was considered a safer way than binary as source could contain a copyright notice.
*7 - Literally "No Plaintiff - No Judgement", meaning that there are no consequences if noone raises a claim.
*8 - The very same reason why in all those MS products the booklet containing the disks or CDs are shrink warped in clear plastic with the relevant EULA terms readable from the outside, including a (usually bold) statement that opening means agreement.
*9 - That is outside the adult rank :))