You do have the ability to use Github without revealing your identity. I believe developers using Tails OS can code conveniently. What tools do you require? Programming software can be stored in persistent storage. Each commitment is automatically submitted through Tor.
This is a requirement for any developer who chooses to enhance anonymity nowadays.
If it is possible, it doesn't mean it will remain possible. Github is still centralized and can change its rules in a blinking of an eye like coming up with some excuse and banning Tor.
Not to mention that the problem with centralized Github is also the code/repository itself that can be purged from their servers without prior notice if the order comes down from the US government. They have already done it once at a large scale about 5 years ago, who's to say they're not going to do the same to for example Samourai-wallet-like projects?
Does this have to do with Saylor's new decentralized identity proposal? Yes, it's just PGP, but more complicated.
Yes that's what @takuma sato said.