Is this word still capitalized when it is used as a verb?
Example: "Welcome to our house."
'willkommen' is only capitalized at the beginning of a sentence, like 'Herzlich willkommen' versus 'Willkommen in meiner neuen Wohnung'.
You don't capitalize verbs, except if the are use at the begenning of a sentences (how Menschenkind said). All substantives are capitalize doesn't matter where in the sentences it is