Poet Helmut Seethaler came to some local fame in Vienna during the 1980ies, when he printed his poems on small slips of paper and fixed them with adhesive tape between two trees or lamp posts, where they could be "plugged" by the passers-by. He fought endless battles with the police, who sued him times and times again for "spoiling public places". Now he apparently uses form boards at construction sites (like this particular one at Praterstern) as media for his poems.
This one translates as follows

Those who have more
must not get even more,
because otherwise
those who have less
will soon have nothing at all.