r4a.org
Three causes with large, organised, well-funded constituencies all reduce to these characters, which is unusual for a string this short.
Animal rights organisations operate in every country with substantial public support and reliable individual giving. Open access campaigning has institutional backing from funders and universities arguing that publicly financed research should be publicly readable. Development work across Africa attracts multilateral and philanthropic money at scale.
Research for all, rights for animals, resources for Africa. Each is read correctly on sight by its own sector, because the four-as-for pattern has become the default way institutional programmes are named.
That is inherited legibility. A new organisation adopting the shape starts out looking like it belongs rather than looking like it needs explaining.
Three characters, the extension the whole sector uses, and no mechanism by which more become available.
The name is available. Offers welcome.