Rikodou chakra is basically the chakra of Rikodou Sennin, Hagoromo. And probably Hamura too.
It can be attained in different ways (as shown in the manga):
1. Inheriting it from Hagoromo (Indra and Ashura's case)
2. Directly receiving it from Hagoromo (Naruto and Sasuke's case)
3. Or by combining Indra and Ashura's chakra to form it (Madara's case)
Note that all Rikodou chakra will not be of the same type. For example, Indra and Ashura had Yin and Yang Rikodou chakra respectively which are different types of Rikodou chakra with different potency as well. Although Rikodou chakra is one with no disparity in type generally, its Yin and Yang constituents can differ in properties, as shown with Indra and Ashura as well as Sasuke and Naruto.
Also, not all Rikodou chakra of the same type will have the same power or potency. It depends upon how mature they are. For example, Rinnegan Madara may not have the same chakra potency as Hagoromo despite having the same exact chakra.
Now coming to the question of how a JJ like Obito can have Rikodou chakra. Well, Juubi's chakra and Hagoromo's chakra are essentially the same type of chakra, they are more closely related than you think. Kaguya is basically the Juubi, so naturally, her chakra is the Juubi's chakra. Hagoromo being Kaguya's son means that he inherited the same chakra i.e. Juubi's chakra. It may not be similarly powerful but it is definitely the same TYPE of chakra as the Kaguya i.e. Juubi. Which is why becoming a JJ will grant you Rikodou chakra and Rikodou Senjutsu.