These are native Spectrum homebrew games, not the historical commercial Tetris release.
JSSpeccy 3.2 by Matt Westcott: upstream, GPL v3, complete corresponding source. Emulator binaries and bundled firmware are unmodified from the upstream release. The player.html integration is GPL-3.0-or-later; its source is the served HTML itself.
Tetris 1.00 © 2019–2020 David Crespo: source, MIT license.
CSSS by TheShich: upstream, GPL v3, complete corresponding source. Runs in 48K compatibility mode. Press R then ENTER to RUN; two players tap CAPS SHIFT and SYMBOL SHIFT.
Files loaded using LOAD FILE stay on your computer; they are not uploaded.