For a few months now, we've been mirroring a selection of game prototypes at @HiddenPalaceOrg - you can download, inspect and read about them at hiddenpalace.org but you can play them in your browser at the Archive! archive.org/details/hidden… 
The work and effort that Hidden Palace is doing to find these thought-lost prototypes and never-released carts and programs is Herculean - they often do releases in bulk or in themes and they document what's so special about them or what changes they lack from the releases.
Just to address: Why are they "Stream-Only"? Because the volunteer who's been working on this material sometimes has to do adjustments to the archives to make them emulate in browser, so to avoid making messed-up "cooked" versions generally out there, we redirect to HiddenPalace.
