File management: what open and free software do you use to manage a large collection of photos?

What is the best software to manage photos? I know this is a question that has been asked in the past, but I want to add two restrictions:

  • Open format. If in 50 years someone wants to see the photos I took, I want them to be able to extract the metadata from my photo, regardless of whether the software I used to label the photos exists or not.
  • Free. I can not imagine paying a monthly fee to Adobe for the rest of my life. The day I stop paying, I lose the metadata.
  • It works in Windows.

I really like to use Lightroom 5, but I'm worried that Adobe in a few years will tell us that we can not use it anymore ( -demand-to-use-old-versions-of-photoshop).

Over the years, I have taken more than 30,000 photos and would like to be able to label them all with the confidence that the labels will not be lost due to a software license.