Bummer about the loss of your friend.

Do you have the equipment, space and a secure location to pull-off a sucessful grow?

If you're an inexperienced grower, you might want to save 'em for when you have more knowledge about the breeding processes. Otherwise, you risk degrading the qualities in the strain(s) that your friend wanted to preserve.
I'd grow one strain at a time, so you won't risk cross-pollination. (hybridizing)
But if you're not going to offer them to the public, (via sedbay or as gifts) then cross-breeding really doesn't matter right now. But down the line when you've gained more experience, you'd likely regret not keeping the strains intact.

As long as the seeds were kept cold and dry, (as others have mentioned) at least some ratio of them should still be viable. They might need some extra TLC to get going, but once they do you should be fine. I'm not too sure I'd re-freeze 'em if they've been thawed though. Speeking from inexperience with that particular situation...I have no clue what the result would be. Might just be fatal though...

How were they packaged? If just tossed in a Ziplock for 20 years, freezer burn is possible and likely. Bummer he didn't know the strain names.
Rusty Trichome Reviewed by Rusty Trichome on . 20+ year old frozen seeds I looked around for anything similar to my question in these threads but could not find anything remotely close. (I could have missed some threads, though.) I had a friend pass away recently who had kept seeds from the best weeds they had smoked starting in the mid '80s - early 2000's. They kept them frozen. They didn't note the strains or anything more than, "kicked ass" - "mellow" - "couch potato locked" - "fucking unbelievable high" etc. so I have no way of knowing what percentage of Rating: 5