''Write'' sounds more like a command. Why is this habitual? What are they trying to say with this? Somebody usually writes? I don't get it.
This is one of the many useless sentence fragments with no context in this course. I hope some day they fix this all up.
The habitual form tells you that it's something done on a regular basis, as a habit, or a general statement about a person or a thing. Like when we say "birds fly" as a general statement about birds. In Swahili it would be "Ndege zaruka".
And what I did there was to mix the habitual and the gnomic verb form. The last part about general statements is actually the gnomic and not habitual. They are similar in function but distinct forms.
Actually it's more like 'writes'. It could be a response to a question as in "What does she do after coming back from work ?" 'Huandika'
The duo notes say that the 'hu-' form must always be preceded by a noun or personal pronoun, because, presumably, it does not take a subject prefix. Thus 'husoma' could equally be a translation of 'we write' or 'they write' for example, because there is no subject. I hope I'm right - it's the first time I have queried the Swahili.