2 official rulings from Bandai. Straight answers to how this card actually resolves.

If multiple Digimon with the [D-Brigade] are played at the same time. Does all of them gain <Rush>?
Yes, all of them gain <Rush>.
If a Digimon with [D-Brigade] and a Digimon without [D-Brigade] are played by the same effect. Do both Digimon gain <Rush>?
No, only the Digimon with [D-Brigade] will gain <Rush>.
Got a line that uses Sealsdramon? Map it in the builder and share it with a link.
Questions and answers are Bandai's official rulings, collected and translated by the DigimonCardGame Wiki community and reused here under CC BY-SA. Card names and card text are © their respective publishers; Combalo is not affiliated with Bandai.