While I had openshot open, not necessarily rendering or with a project
open, I wasn't able to shut off my screen and keep it shut off for
more than a few seconds with normal DPMS commands (eg, 'xset dpms
force off').  Once I closed openshot, my screensaver functioned
normally.

I couldn't find anything obvious in the source (eg via references to
xdg-screensaver, xset, *screensaver etc), so it's probably buried deep
in a library somewhere, but a userspace program has no business
deciding such policy.  Especially just a video renderer, not a video
player.

See also an old bug #374644 for xine where they had similar craziness
with screensavers.  I really hope openshot isn't faking a keystroke!