building dropbox is not straight forward, it will require python, no problem we have an addon that you can install
but it it also need pygtk module. That is currently not compiled with our python version so it will need to wait. Another issue is that it needs nautiles-extensions lib. That part i can trick during compile but I doubt if then dropbox will run as it should. it seems this application needs the gnome desktop (our nas doesn't has a desktop to run).
Anyhow it will not be a quick solve. When I have more time I will try to recompile python to include gtk
But please do some study on the internet to find out f it can be used on a nas at all. I don't want to spend my free time useless ;)
for the moment this
https://github.com/andreafabrizi/Dropbox-Uploader could be what you are actually looking for
also the already integrated BTsync is a good alternative and read this
http://www.extremetech.com/computing/18 ... re-dropbox