From memory, the other popular domain name extensions were taken at the time.
Dharma Wheel (the Mahayana/Vajrayana one) is dharmawheel.net
If we had first dibs at all the domain names ever invented it would be easier... but in the absence of that, we have what we have. I think the complete absence of ads and paid memberships is sufficient to demonstrate that the site is not-for-profit.
"Do not force others, including children, by any means whatsoever, to adopt your views, whether by authority, threat, money, propaganda, or even education." - Ven. Thich Nhat Hanh
"Whether I were to preach in brief, Sāriputta, or whether I were to preach in detail, Sāriputta, or whether I were to preach both in brief or in detail, Sāriputta, rare are those who understand." (A I 333, Sāriputtasutta)