Generally you can't make something an open standard if it is encumbered by burdensome patent requirements which given the actions of the patent troll, I'd say there is burdensome patent requirements that would require someone to pay those license fees. Who knows if they truly went to make it an open standard* but the moment that patent case showed up any process would have been put on hold and when they lost it essentially would have killed it entirely.
To work around the patent, Apple had to re-architect FaceTime to move from being a peer to peer platform to rely on a relay server hosted by Apple. An
Ars Technica article from 2013 covered how Apple moved to 100% relay servers otherwise they'd be liable for royalty payments on it. At the time of the article, Apple was paying $2.4 million per month to run Facetime's relay servers. The article mentions that previously only 5% to 10% of the calls were running via the relay with everything else being peer to peer. That meant they didn't have to pay for the majority of the traffic so that's a much cheaper bill to foot if you're going to help host and make it a cross platform reality. I can only imagine that cost has increased over the years and if they'd truly opened it up to everyone it'd be even more again.
* I'm inclined to believe that Steve wanted to make it an open standard, it's actually a fit for his personality.