Gooseneck loosestrife and many other species of Lysimachia can be aggressive spreaders under the right conditions but are by no means considered "invasive". A more appropriate terminology might be "thuggish" :-) They do not spread to natural areas or threaten native plantings and can be easily controlled by removal or by planting in less than ideal conditions. This plant in dryish shade for example is very well-behaved and a great garden addition.