Traditionally 'kolonihaver' were intended for recreational use and vegetable gardens for workers living in apartments in the larger cities. You were not allowed to live there full time and you should always have an ordinary home beside it.
Unfortunately the rules are not followed, and for a very large part they get used as a small property with a tiny house for the whole year. Not really for recreational use or growing vegetables - mostly for living cheap in expensive cities. I say unfortunately, as living in them are clearly an tax evasive action.
No property tax is payed, while their values rises like most ordinary properties. The Danish property tax is intended to tax the value gained by increasing property values. So when you live in one of these kolonihaver this way you are doing tax fraud. Even though it's mostly never investigated and punished.
It easily gets glorified as a smart and cheap way of living, when you present it like this in a blog post shared on a global forum(HN). But unless you voluntarily pay tax on the monetary gain you'll have the day you sell it again, I despise your lack of contribution to, and participation in, our Danish society.