We expect that post-singularity there will still be limited resources in the form of available computational resources until heat death.
Those resources do not necessarily need to be allocated fairly. In fact, I would guess that if they were allocated unfairly the most like beneficiaries would be those people that helped contribute to the creation of a friendly AI.
Now for some open questions:
What probability distribution of extra resources do you expect with respect to various possible contributions to the creation of friendly AI?
Would donating to the SIAI suffice for acquiring these extra resources?
Personally, I expect the FAI to give a baby universe to everyone who wants one, so the question is moot.
If not, I do not expect the FAI to care about past contributions, since its goal would be to maximize something like integral of (fun*population) over time, so the people with the highest fun/resource ratio would be rewarded, most likely those with the lowest IQ, as they would be happy to be injected with the fun drug and kept in suspended animation for as long as possible.
I don't know what I expect but that is certainly what I want it to do.