The word closest to 'dharma' is 'duty', social, national and human. To help others is a duty, to take care of the family is a duty, to do things which help your nation is duty, to follow the traditions is a duty, to be respectful to weak, women and children is a duty. And the duty should be performed fully - manasa, vacha, karmana - in thought, in speech and in action. Same in Hinduism as in Buddhism. Traditions are not fixed, they may change over time according to need of the times. God/Gods are not involved in duty, they are peripheral. Gods also will not say anything otherwise. The theist will have the same duties as an atheist, being part of the same society. That is why 'dharma' is said to be eternal.
Thank you.
Its worth noting the various unsucessful attempts to translate the word into different languages.
There have been numerous, conflicting attempts to translate ancient Sanskrit literature with the word dharma into German, English and French. The concept, claims Paul Horsch, has caused exceptional difficulties for modern commentators and translators. For example, while Grassmann's[24] translation of Rig-veda identifies seven different meanings of dharma, Karl Friedrich Geldner in his translation of the Rig-veda employs 20 different translations for dharma, including meanings such as "law", "order", "duty", "custom", "quality", and "model", among others. However, the word dharma has become a widely accepted loanword in English, and is included in all modern unabridged English dictionaries.
Dharma - Wikipedia
The word of course is emphasised in the discourse between Arjuna and Krishna as recorded in the Bhaghavad Gita.
In the name of dharma, Arjuna argues for nonviolence by assuming that to attack and kill so many leading men, nearly all of whom are fathers and husbands, will destabilize the important families and communities for which these men are responsible. The families themselves are vital to the peace and virtue of society. Arjuna’s argument, literally translated, proceeds as follows:
On destruction of the family, the perennial family dharmas perish. When dharma perishes, adharma [the opposite of dharma] overwhelms the entire family. From the predominance of adharma, O Krishna, the family women are polluted. When the women are polluted, O Varshneya, a confusion of social orders arises. This confusion leads only to hell both for the destroyers of families and for the family. Certainly the forefathers fall [from heaven] since the ritual offerings of food and water are suspended. By these crimes of the family killers, who propagate a confusion of social classes, community dharmas and the everlasting family dharmas are devastated. We have always heard, O Janardana, that those men who devastate family dharmas have their residence fixed in hell.
—Bhagavad-gita 1.39-43
Lord Krishna is about to teach His friend Arjuna that above even dharma is God, who, for His own reasons, desires this battle. Lord Krishna rejects Arjuna’s argument as mere “weakness of heart” (hridaya-daurbalyam) and “impotence” (klaibyam) and urges Arjuna to fight.
Despite his previous arguments on the basis of dharma, Arjuna now admits that he is actually “confused in mind about dharma” (dharma-sammudha-cetah).(Bg. 2.7)
Arjuna then gives up his arguments and surrenders to Lord Krishna as his spiritual master, and Lord Krishna begins teaching the Bhagavad-gita in earnest.
Lord Krishna does not at once address Arjuna’s argument about dharma, as we would expect in a typical debate. Rather, the Lord first reveals to Arjuna, in twenty verses (Bg. 2.11- 30) the eternal nature of the soul. Then the Lord comes back to the topic of dharma, to show that it is Arjuna who is neglecting his dharma by refusing to fight:
“And even considering your personal dharma as well, it is not right for you to hesitate. There is nothing better for a warrior than a fight based on dharma.” (Bg. 2.31)
Lord Krishna concludes this brief reference to dharma as one’s personal duty by saying,
“Now if you do not execute this battle, then having given up your personal dharma and reputation, you shall incur sin.” (Bg. 2.33)
Lord Krishna again speaks of dharma in the ninth chapter when he declares that spiritual knowledge of Himself is dharmya, or conducive to and consistent with dharma:
“I shall speak to you, who are free of envy, this most confidential knowledge, together with its realized discernment, knowing which you shall be freed of the inauspicious. This knowledge is the king of sciences, the king of secrets, and the supreme purifier. Understood by direct perception, it is conducive to dharma, very easy to perform, and everlasting. People who do not place their faith in this dharma, O burner of the foe, do not attain Me but return to the path of death and material existence.” (Bg. 9.1- 3)
Now that Lord Krishna has explained “this dharma” (asya dharmasya), which leads to His eternal abode, we can better understand Arjuna’s statement in the eleventh chapter that Lord Krishna is the protector of
“everlasting (shashvata) dharma”: “You are the indestructible, the supreme object of knowledge. You are the transcendental receptacle of this universe. You are inexhaustible, the protector of everlasting dharma. I conclude that You are the eternal person.” (Bg. 11.18)
The eighteenth and final chapter of the Bhagavad- gita summarizes the entire text. In this chapter Lord Krishna refers three times to dharma, the first being a reaffirmation of His earlier admonition to perform one’s own, and not another’s, dharma:
“It is better to engage in one’s own occupation, even though one may perform it imperfectly, than to accept another’s occupation and perform it perfectly.” (Bg. 18.47)
But beyond this, we have seen that the Bhagavad- gita begins where ordinary Vedic dharma leaves off. Lord Krishna has indicated this in various ways. Here, at the end of His teaching, the Lord most dramatically declares that full surrender to the Supreme Lord stands above the entire range of sacred duties known generally as dharma:
“Renouncing all dharmas, take refuge in Me alone. Have no regret, for I shall free you from all sins.” (Bg. 18.66)
Adapted from:
Dharma in the Bhagavad-gita | Krishna.com
The discourse develops the understanding of Dharma from well known Vedic texts. It encompasses both service/duty and devotion to Lord Krishna.
As you say there are different perspectives of Dharma depending on theism or atheism.