From what I'm reading these Free games are for keeps. Usually if the games are free for a limited time, it will show up with a timer beside the game.
Not exactly free, but today for some reason steam decided to randomly give me a 75% off coupon for Valkyria Chronicles, which I already own. So if anyone wants it, shout out. First come first serve.
In celebration of their 30th anniversary, Ubisoft is giving away one of their games for free each month for the rest of the year (7 total). The first one, available for free now, is Prince of Persia: The Sands of Time. Here's the 30th anniversary page where you can get the free game of the month. Note: You have to have a UPlay account to claim the free game. You also need to have the UPlay application on your computer to download it.
Humble Bundle is providing abstract space tactics game SpaceCom as a free DRM-free download. https://www.humblebundle.com/pc-android-14-bundle (towards the bottom of the page)
Apparently the original version of Destiny is now free to play on Xbox and Playstation... I'm not sure because the PS4 version says it's a demo or a trial. https://www.microsoft.com/en-us/store/p/destiny/c2jqrc2c49b0
it is basically a demo version, AFAIK it's the story progression on Earth (4 or 5 missions?) with a level cap of 7, no PvP
oh wow, they extended the trial! that's actually pretty cool and should serve as a decent rough impression for the overall content
Well, Reddit isn't convinced? https://www.reddit.com/r/DestinyTheGame/comments/4yzd0x/destiny_is_now_free_no_dlc/
Seems to be conflicting info right now. http://rectifygaming.com/destiny-potentially-going-free-replacing-trial-version/