As others have noted, it's free-with-ads (at least in the U.S.) on IMDbTV, which is also available via Prime Video — and even with a free Amazon account (even without Prime membership) you can watch the show through the Prime Video web interface here:
If you are in the US, fringe is free to stream with amazon prime or imdb freedive.
https://www.amazon.com/Fringe-The-Complete-First-Season/dp/B001FVV2X2
To clarify, Amazon Video still has it available for streaming purchase, but it is no longer part of Prime Video (i.e. free for Amazon Prime subscribers).