I hope everything you are going to develop, would be free to use inside Wikimedia Projects and Tools.
Topic on Talk:Wikimedia Enterprise/Flow
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In Telegram chat @Seddon (WMF) said "The team is also working with Wikimedia Technical Engagement to add free community support through cloud services by June 2021. In the interim, access can be provided on a per-request basis." I'll let Seddon elaborate.
Addendum: Found a link to that here m:Wikimedia_Enterprise/Essay#Free_access_for_some_users
FYI - what @Fuzheado said here is correct. As an update - you can follow progress on this ticket