Trial Game key

No, it isn't. It wouldn't make much sense to giveaway those regardless, though.

From the SG Guidelines (I recommend reading them):

Giveaways
Creating
• Beta keys which do not provide unrestricted access to the full game in the future, guest passes, demos, and coupons cannot be given away.

In other words, no, it's against the rules.

https://www.steamgifts.com/discussion/91siP/trial-games

While it is really recommendable to scan through the full site rules at some point, it is at the very least worth reading up on the site's grounds for suspension, located at the bottom of this page, for the especially key considerations to keep in mind. For this particular matter, refer to the following suspension premise:

Gifting Beta Keys, Guest Passes, or Coupons - [Suspension Length:] 3 days

Thanks for the answers everyone. I made a support ticket as i wasn't sure. The person who made the giveaway probably knew it was a trial key.

You cannot give out beta keys, although some people might not mind getting the closed beta and trying something new for themselves, but according to the site rules, the keys to the beta version cannot be handed out