Although they are primarily intended for, and designed for the purposes of, high-volume commercial organisations, the API suite IS open source, like all WMF software.
Also, it is not gated for only people who pay - accessible to anyone (including for commercial purposes) via its own website - at no cost. The payment comes with higher volume usage requirements and/or SLA contractual guarantees. Furthermore, there are alternative access methods especially for wikimedians, notably via WMCloudServicies. If none of that works for you there is also a published criteria method for requesting exceptional access to the higher speed/volume for - exactly as you mentioned - mission-aligned reasons.
These access methods are documented here: https://meta.wikimedia.org/wiki/Wikimedia_Enterprise#Access

If we ever end up in a scenario where a contributor feels compelled to pay for a Wikimedia Enterprise account, we have done something seriously wrong.

I'll also link to the operating principles of the project here: https://meta.wikimedia.org/wiki/Wikimedia_Enterprise/Principles which, among things I've already mentioned, include a specific element which addresses, and guards against, that concern. 

You can read the FAQ with sections about finance, tech, legal, and strategy/mission alignment  here: https://meta.wikimedia.org/wiki/Wikimedia_Enterprise/FAQ
If you have any further questions about that API suite - please come over to the talkpage on Meta wiki.

I do not wish to distract the mailing list from the larger points being made in the discussion on this thread - just to clarify these specific side issues. 
Sincerely,