Hi,
It indeed seems that the business was bought by Klarna.
However, we're not Germans and can't read what's written here:
www.klarna.com/sofort/
From what I understand, you can still use it. You just need to create a merchant account there.
Please note that this plugin was not developed by us but by a third party company for Sofort.
The plugin wasn't working properly, so we had to look into it to be able to provide a working version that you can use. However, we're not familiar with Sofort and since most of what is relative to it out there is in German, it doesn't help. The best is to contact Klarna support to check with them what they recommend.