A friend of mine once told me that if the Java fern is producing keiki (babies) on the leaves, it's because the water quality isn't good enough...don't know if it's true or not but some food for thought.
My java fern rarely produces any keiki on the leaves, it only did when I first started my tank and the water wasn't "settled" yet. Since my tank is about 6 years old, my java fern grows like crazy by growing rhizomes and not keiki on the tips of the leaves.
When my ferns did produce little keiki like that I would just leave it until it got bigger then I would just gently pull it off and re-tie it to a piece of driftwood.
Just give your plant some time and it should start to grow and attach itself to the driftwood. Java fern doesn't require alot of light to grow so maybe it's just your water quality. If I'm wrong someone please correct me.