Are free-nuclear division and endomitosis the same?
No. If you google the terms you'll get a lot of sites with definitions. For example:

Nuclear division
Definition
noun
The process by which a nucleus divides, resulting in the segregation of the genome to opposite poles of a dividing cell.

source: http://www.biology-online.org/dictionary/Nuclear_division
Edit:
or

free nuclear division    mitotic division of nuclei without accompanying cytokinesis, i.e. nuclei divide in a common cytoplasm, the cells walls only forming around each later

source: http://ecflora.cavehill.uwi.edu/bio_courses/bl14apl/Gloss.htm
versus

endomitosis
mitosis taking place without dissolution of the nuclear membrane, and not followed by cytoplasmic division, resulting in doubling of the number of chromosomes within the nucleus.

source: http://medical-dictionary.thefreedictionary.com/endomitosis
or a bit more revealing:

Duplicated chromosomes produced by endomitosis exist as discrete units
in a single polyploid nucleus or may be packaged into separate nuclei,
depending on the phase at which mitosis is aborted

source: http://en.wikipedia.org/wiki/Endoreduplication
So as you see by definition nuclear division is part of a bigger process (cell division), and accoriding to the first source karyokinesis is a synonim for nuclear division (karyo = nucleus kinesis = moving, both come form greek language).
Edit:
If you check the definition above, you can see that free-nuclear division is a mitosis without cytokinesis, thus chromosome separation still occurs.
In endomitosis the can end up with a polyploid nucleus, in contrast to the other two aforementioned mechanism where no polyploidy occurs.