Can you tell me please what happens when a Non Profit Organization makes a profit?
This is actually a tricky one. Given their legal status they are not allowed to make a profit from any commercial activities, so it is a moot point whether they are permitted to run a "for profit" clinic. Yet this is what they are demanding to subsidise their charitable work.
If they are permitted to run a "for profit" arm to their activities, that arm cannot use donated drugs and money without being charged appropriate commercial rates (and possibly not at all, depending on the terms of the gift). And it has to pay a share of the general costs of the "business". As a business centre it is subject to all the normal taxation provisions so it has to be accounted for separately, which given the scale of the operation is an administrative nightmare. I suspect that in practice it would just be swept under the carpet, which is fine until someone from the tax authorities spots it.
Something I forgot to say - a "for profit" clinic run by SAGA will be subject to all the legal and professional constraints put on commercial vets. They will not be allowed to use out-of-date drugs, they must use appropriate drugs and anaesthetics, they must have appropriate equipment, they must operate in all ways according to veterinary "best practice". Procedures that "got by" in the past will not be permitted in the future, now that there is a "proper" vet available. In demanding to have their own vet permitted to operate commercially I don't think they know what they're asking for.