there are no popular alternatives. Either you are super smart and design one from scratch… or you stick with OAuth and hope that some of the addressed problems will be resolved.
If you're consuming an API you use whatever the platform decides on. In that case, this library is helpful. However, I think the real open question is: if you are providing an API, what do you choose?
I think at this point you choose either OAuth 1.0a or to roll your own. If it's not in your future to be a public API, I'd go with rolling your own if you are comfortable writing that kind of code.