I was both Alpha being quasi-open itself, like OpenPOWER today, and like earlier PDP minis had been, whereas VAX had been pretty locked down, and OpenVMS getting POSIX compatibility (admittedly probably more the latter than the former, but DEC was big on branding things "open" at the time, partly because they were losing ground):

https://www.digiater.nl/openvms/decus/vmslt05a/vu/alpha_hist...

> Although Alpha was declared an "open architecture" right from the start, there was no consortium to develop it. All R&D actions were handled by DEC itself, and sometimes in cooperation with Mitsubishi. In fact, though the architecture was free de jure, most important hardware designs of it were pretty much closed de facto, and had to be paid-licensed (if possible at all). So, it wasn't that thing helping to promote the architecture. To mention, soon after introduction of EV4, DEC's high management offered to license manufacturing rights to Intel, Motorola, NEC, and Texas Instruments. But all these companies were involved in different projects and were of very little to no interest in EV4, so they refused. Perhaps, the conditions could be also unacceptable, or something else. Mistake #5.

> Wasn’t the “open” at the time meaning “open system” as a system that is open for external connections (aka networking) and not so much open as in “open source”?

Networking was the initial impetus, but the phrase came to include programming interfaces, which is why POSIX was considered such a big deal. The idea was to promote interoperability and portability, as oposed to manufacturer-specific islands like those from IBM and DEC.

No, it meant industry standards, instead of proprietary ones, that is why POSIX, Motif, and others are under The Open Group.