While I don't have anything to say in the openastronomy discussion, I want to say that I would support this group.

Where is the open source software component here? The definitions for addition to OA are not finalized, see other open PR and relevant discussions, but OA was always about open source, preferably openly developed software and the github link of this is an empty organization.

HEACIT is newly formed (about 3 months ago), thus there is nothing to show in github yet. From the linked mission statement above:

The HEACIT collaboration is a working group that seeks to identify how the landscape of astrophysical software enables or can improve the impact of high energy astrophysical data. This includes maximizing the return of current and future observations, as well as increasing their usability and interoperability with datasets at other wavelengths.
HEACIT is not technically associated with any particular software package, but HEACIT members include developers of high energy software packages such as XSPEC, SPEX, Sherpa, and ISIS. The goal of the working group is to connect developers, align on standard practices and collaborate on future development, while allowing for and preserving the diversity of available high energy tools and workflows.

So, it's about open standards and making high-energy tools more interoperable, which will include some newly developed software, but its fair to argue that, at least at this point, HEACIT itself is not primarily a software development organization; however, it will clearly support a number of software packages, some of which are open source and some of which are not. One of those packages is Sherpa, which is already an OA member.
In our view, HEACIT is clearly an organization about software; it supports open source software (although some of the individual HEACIT members also support non-open software), and it works on open standards and APIs. That seems to be well aligned with the OA mission "to share resources, ideas, and to improve code." (from the OA landing page)
We could not find a written definition of the requirements to become a member of OA, but the current members list contains organizations that do not seem to be primarily software developers, such as the Italian Mars Society.

One of the first things that HEACIT plans to do, is so collect a set of test data, so that all high-energy software packages can test their IO (and in a later stage also their fitting routines) against a common set of files that is more complete than what individual packages typically use (e.g. Sherpa CI tests extensively against Chandra and some XMM, but no e.g. NICER or BeppoSax data).

If the OA owners find this application for membership insufficient, please let us know what the membership criteria are or what additional materials HEACIT can provide (e.g. meeting notes, memberships lists, planned development).

Moritz has presented a very nice argument for our group. While we aren't a particular software development group, we aim to support open source software projects and provide infrastructure for community discussion. Projects like the one Moritz mentions -- providing an example set of high energy datasets to support software developers -- can and will be documented in an open source way. Our group is only beginning, and we are looking for OA membership in order to advertise our work and build a community resource on Discourse.

the discord in my view is a totally separate thing than the membership page, which has a very strong focus on software. You may spot a few non code looking ones, but the fact is that even those participated as various summer coding programmes, or have been added in the very early days of OA and member removal procedures hasn' been implemented.

Bottom line, I OK with using the OA discorse and getting tags for those discussions for findability, etc, but adding one extra non software layer into OA still doesn't make much sense to me, especially when some of the open source software you plan to support is already OA members with an existing track record of participating in the programmes that we run.

I am one of the Discourse moderators, and I discussed the idea of opening a Discourse page for HEACIT in our Slack channel. There, @Cadair said that it be more appropriate to apply for membership in OA as a way of obtaining permission to use the Discourse server.

Bottom line, we are getting conflicting messages, so I would like to hear from more people. Does OA have a decision making body that meets to discuss these things?

PS - I do not want to be dismissive. I understand @bsipocz 's points, but I want to be sure it is a community based decision. I want to avoid a situation where where I start activity on Discourse, and then I receive messages from a separate person saying that our activity on an OA supported server isn't warranted.

Thanks for the consideration. I am taking this conversation as permission to start a HEACIT page on the Discourse server. I will close this PR in a week or two.

A bit late to the conversation - sorry @eblur.

First of all, thanks for considering being part of OA!!

Does OA have a decision making body that meets to discuss these things?

Yes, we do... However, we've not met in a long time (before Covid) and that's clearly a problem. I wouldn't close the PR so that the OA steering committee meets and discuss this point. I'll try to organise a meeting soon and inform on this PR of the decision.