The question of DOT compliance is interesting since it’s the bulb.
I've never heard that. Everything I've ever read says that both the housing and the bulbs must be marked with a DOT stamp to be legal.
Luckily, I live in Oregon, which didn't require headlights to meet national DOT standards until something like 1999. I can always feign ignorance and say the car came with the Depos, so long as they meet Oregon's old, state-specific lighting and alignment standards.
ORS 816.030 made it an offense to sell non-complying lighting equipment. There might be a harsher federal penalty, too. Depo probably just needs to label them as "offroad use only", but the limited sales probably aren't worth the effort.