You can play with various versions of UNIX from UNIC v0 to SVR3 and BSD at https://unix50.org through SDF Vintage Systems. Additionally, access to Multics as well as other various historical operating systems is available through their museum.
If you visit https://wiki.livingcomputers.org/ you can learn about many of the remote systems that continue to operate. They are a mix of 18 real hardware and emulated systems with guest access, if you don't have a personal account. The wiki is also contributed to by the community of users that use these systems. In there you'll find code examples and user documentation regarding these historic systems.
For those who may not know about SDF, here is some background that might be helpful. While the user experience these days is quite different than it was in 1987 or even into the mid 1990s, the philosophy has always been focused on UNIX as a multi-user platform for doing what the community wants with it. As a result, there is a very long authentic history and unbroken continuity over the past 35 years which you can still sense when you login and participate in the community. Many of us here (hacker news) use the UNIX shell daily and it is part of our work flow as users, developers and system administrators. Before dialup SLIP/PPP was wide spread (way before cable modems or DSL) the user experience was solely in the shell from their PC or just a terminal with a modem at home. Terminal based utilities such as elm (mail), trn (usenet), telnet, ftp along with useful informational diagnostic programs such as ping, traceroute and whois gave you a glimpse into those diverse systems that made up the internet. In the early days of the web/gopher the bar was lowered significantly and a lot of new folks started to understand what we were doing. We grew!
SDF spawned a handful of commercial internet service providers in Texas although SDF remained independent of them. MetroNET was the first one and lasted up until the dot bomb when it was acquired by Internet America. SDF likely survived the dot bomb due to its community rather than being commercial with customers. By 2004 once facebook really started to take off, using the shell to do anything, specially to new folks, seemed antiquated and 'retro' or even criminal, but it still clicked with folks that there was an immediacy of access to text and the UNIX toolkit that kept it fast and simple. internet community wise, I suppose it was the height of phpforums and cheap (though banner laden) webhosting and the rise of more centralized social networking honeypots. While USENET may be the original fediverse (and we still have USENET) the interface that facebook/myspace/twitter offered was something folks wanted on SDF too. And because we're just a platform, we can build on it. StatusNET/GNU Social/Diaspora/Elgg were things we could try without negatively affecting the community: no one was forced to "upgrade" to Diaspora, it was just another feature. If social networking wasn't your thing (or still isn't) then its not required to use SDF. However, I'll say I'm really happy that Mastodon, Pixelfed and Peertube have really gotten a foot hold. Federated platforms like those allow us to use the internet in its most natural way. I believe they'll continue to make strides, though there are likely always going to be brief phenomenon like "vine" or "tik-tok" that take advantage of people.
So in using SDF, you may run into cool subsystems, friendly users, grumpy users, fun programs, user contributed tutorials and various corpses of tried projects (oh, there are nethack bones files going back into the 1990s btw), but hopefully you'll find that there is a unique and authentic spirit in its community that seems to endure and continues to be built upon.
The Australian experimental electronic band Severed Heads has released a playable compact disc that has an analogue record groove. The CD plays in a normal CD player, but flip it over and you've got about 3 minutes of a record that ends in a locked groove loop. The band is setting out on a tour of North America with Front 242 next month.
Celebrating 30 years right now at the Vintage Computer Festival being held at Computer History Museum in Mountain View California. Can't be there? join virtually: ssh [email protected] and choose option 1.
One of the big features of SDF is the MetaArray. it gives members around 800GB per account of storage both NextCloud and direct shell access https://sdf.org/?tutorials/metaarray
SDF has a free streaming music service called aNONradio with live (including daily openmic) and archived content. A handful of its members produce original content shows available at http://anonradio.net