Is this plugin still “in active development” per the banner?
Any ETA for when it might be safe to install in a “production” environment?
Hello and welcome @Firefishy 
Post Voting is still described as in active development but should be okay to install into a production environment. 
I know of a few people already using it. However, it does have some known outstanding quirks if you browse the post-voting tag to familiarise yourself with them and see if any are currently deal-breakers for you.
Almost instant update…
The ‘In active development’ note has now been removed. 
It is now classed the same as our other official plugins.