The first (Hillel’s version) is negatively formed – and I have often preferred it
I also consider the negatively phrased version to be much preferable, because positively-phrased ones allow for imposing one's ideology onto others, which never ends well. Also, I would note the Christianist versions at least remain at a first-person level; with the abstraction to all of "mankind" found in the Islamist version ("That which you want for yourself, seek for mankind.") virtually any atrocity can be justified. Other Islamist versions are translated/rendered using "brother", which opens up the loop-hole that non-conforming men simply aren't "brothers" and women are unprotected. The Christianist's "neighbour" seems less prone to being twisted in these ways.
I consider PD31 to be an improvement, because it incorporates a mandate to self-defence, unlike the Christianist's "turn the other cheek" doctrine. (This mandate to self-defence reminds me of the Libertarian porcupine (a mascot loosely analogous to the elephant and donkey), which "[…] was chosen because the porcupine is a defensive animal. It does not shoot its quils (contrary to myth), so it does not harm anyone who respects its boundaries, analogous to the non-aggression principle.")
Michel Onfray incorporated a somewhat more positively formed dictum in his Hedonist Manifesto: “Enjoy and have others enjoy, without doing harm to yourself or anyone else; that is all there is to morality” – especially if one takes that “have” in an active, rather than passive, sense.
I would not like to take "have" in an active sense, because that would make the pleasures of other people my responsibility; something which I am very firmly and vehemently against. If they are able, they can take care of their own pleasures, and I will not harm them. If they are disabled, I will take care of them to the extent that this pleases me. This is inherently ethical, because there is no reason that I should suffer for someone else, and furthermore, receiving "care" from people who are forced to provide it (because they aren't pleased by providing it) ends in abuse of the person in need, even if the one administering the care is an otherwise good person.
...because rather than "personal conscience" I think you can substitute "pleasure." It gives a lot of people "pleasure' to want to make life better for "others in general" - even where you don't have direct relationships with those others.
But as to the general drift of your question as to whether there is anything in Epicurus that would provide some kind of general instruction analogous to a "great commission" to do so, I don't think such a thing would exist because that would come too close to a sort of "idealism" that would be inconsistent with much of the rest of the philosophy. But I think here is plenty of reason for thinking the it enhances your own happiness by making life better for others.
This is a line of thinking I first encountered in Max Stirner's egoism; to quote Wikipedia on that:
"[Stirner] believed that everyone was propelled by their own egoism and desires and that those who accepted this — as willing egoists — could freely live their individual desires, while those who did not — as unwilling egoists — will falsely believe they are fulfilling another cause while they are secretly fulfilling their own desires for happiness and security. The willing egoist would see that they could act freely, unbound from obedience to sacred but artificial truths like law, rights, morality, and religion."
Now, let me modify this excerpt by replacing some key words appropriately:
"[Julia 😊] believed that everyone was propelled by their own pleasure and that those who accepted this — as willing Epicureans — could freely live their pleasures, while those who did not — as unwilling Epicureans, such as deceptive ("modern") Stoics — will falsely believe they are fulfilling another cause [such as virtue] while they are secretly fulfilling their own pleasures. The willing Epicurean would see that they could act freely, unbound from obedience to sacred but artificial truths like law, rights, morality, and religion."
To me, this way of phrasing it, is still quite persuasive and compelling. It doesn't beat around the bush. I'd paraphrase it as: "You'll be going after your own pleasure anyway; by being aware of and honest about it, things can only improve."
Quote from Diogenes of OenoandaSo (to reiterate what I was saying) observing that these people are in this predicament, I bewailed their behaviour and wept over the wasting of their lives, and I considered it the responsibility of a good man to give benevolent assistance, to the utmost of one's ability, to those of them who are well-constituted. This is the first reason for the inscription.
I haven't yet read the inscription; which is probably why I don't understand this: Why does Diogenes of Oenoanda want to help those who are "well-constituted"? Doesn't that mean helping those who don't need help? Shouldn't he want to help those who are badly constituted? Or does he want to help the rich to lead good lives, such that their examples might spread, and their wealth/power not be abused?
Semi-Political Tangent
I think the importance of the Golden Rule cannot be overestimated, because…
- …I think it necessarily leads to a society based on genuinely voluntary win-win exchanges, which I consider a stepping stone to prosperity, freedom, and peace, which in turn I consider to be a requirement for the continuation of the human race due to the advent of the nuclear and genetic age. This is essentially the libertarian anti-capitalist free-market anarchist's perspective also found in Jay Snelson's book Taming the Violence of Faith.
- …I think it is hard to corrupt the well-phrased Golden Rule, because it refers back to the individual's own sensations and feelings, rather than referring to abstract concepts (which are prone to being misconstrued), and in this way can serve as a potent antidote to authoritarian sociopathy, the corruption through power, Stanford-Prison-Experiment- and Milgram-Experiment-esque effects, and so on, if only people's identity is firmly grounded in their philosophical/religious/… system of choice. Which is to say that, when push comes to shove, even a Christianist is less dangerous than someone without a firmly grounded identity. Note this excerpt of what Joshua quoted from Diogenes of Oenoanda above: "the majority of people suffer from a common disease, as in a plague, with their false notions about things, and their number is increasing (for in mutual emulation they catch the disease from one another, like sheep)" That's why rulers like their subjects to have no identity other than as subjects of the rulers, and why the worst cases of indoctrination involve all areas of life that can impact identity formation: schools, media, culture, press, books, …
In short, I consider the Golden Rule as a key element towards a life without "the crimes to which Religion [and institutionalised government and all other forms of unnatural power] leads".
(I hope this tangent is not too political; if it is, moderators please do delete it. I don't mean to cause any drama.)