It's pretty tough to stop this thread from oscillating when the original topic seemed to be 'vintage' and then Berkeley Sockets comes up.
Wow, I did not realize that offhandedly mentioning the socket library was so disruptive. BSD sockets came out in 1983 with 4.2BSD by the way. As in, run on systems like the VAX 11/780, of similar vintage to the PDPs you are discussing. I never had a PC older than an Apple ][e, but I do still have (and use) a lot of old UNIX systems like VAX, Alpha, various generations of Sun, SGI, etc. The concept of networking came around a lot earlier for multiuser systems than it did for personal computers.
As you point out, vintage has a lot of personal meaning. I'm sure to a lot of people even a Pentium II with a 56k modem is "vintage" now. It is pretty hard to decide the dividing line between what is vintage and what is not, since so many things that were created in the 70s-90s are still in use, virtually unchanged. I think of vintage as anything on display on the 2nd floor of the
Living Computer Museum, which by the way is worth a visit, unless mentioning this is also too off topic and is going to send someone into a tizzy.
As far as these projects go, I generally just think of it as trying to construct your own computer around an older architecture (e.g. 68k, 6502, Z80, et. al.). Some people want to recreate the functionality of an entire original machine, some people want to use an original ceramic chip and discrete logic with a rat's nest of breadboard wires, some people (like me) just want to use the old CPU and the rest can go. I have a 6502 game system project queued up where I want to use a modern FPGA as an MMU to do paged memory, use either an FPGA or a DSP for a tiling and sprite engine, have coprocessors for USB mass storage, and output to HDMI at 720p. I enjoy the mix of old and new. I don't feel the need to go back to cassette tape program storage or to try and faithfully rebuild an 8" floppy drive, but I can still enjoy writing the "controlling software" in 6502 assembly, having to be creative with use of memory and cycles.
For technix, the original poster, it looks like he already has some older chips on hand that he wants to find a use for but also wants to incorporate modern components; e.g. the mention of USB OTG and Ethernet.