Basic RetroPGF History
The idea behind retroactive public goods funding seems to have been first succinctly formulated (in the context of Optimism) in July 2021.
Would you like to understand why Vitalik Buterin thought public goods funding should be retroactive, and how any group of badgeholders could be seen as a “results oracle”? Read this seminal blog post.
…And then go read or re-read the Optimism Vision and Ether’s Phoenix.
(If you prefer audio-visuals, you can also check out Karl Floersch’s wonderfully enthusiastic explanations here and here.)
Then you’re off to a great start. 
RPGF Round 1
Round 1 took place in Q1 of 2023. 24 badgeholders were appointed, and 22 of them seem to have actually participated in the distribution of $1M among 76 nominated projects. 58 of the projects received funding.
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RPGF Round 2
Round 2 took place in Q4 of 2021. 90 voting badges were offered, 71 badgeholders selected, and of these 69 actually voted on the distribution of OP 10M among 195 nominated people and projects. All nominees received funding.
RPGF2 was launched alongside with the first iteration of the Citizens’ House. You can read about both events in the announcement below.
Round 2 results - spread sheet
Round 2 learnings and reflections
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RPGF Round 3
Round 3 is taking place now, in Q4 of 2023. OP 30M will be distributed. 145 badgeholders will be voting. More on the selection of badgeholders can be found here.
Projects are this time self-nominated. By the end of the application window there were a grand total of 1596 applications. A separate application review process has been introduced to filter out applications that violate the application rules.
I will add to the info below when more is known about how this round turned out…
Round 3 self-nominated projects
…TBC 