As any open software libre, VLC is open to contributions!
To get and build VLC for Android, check our wiki page.
Concerning VLC core, go to the general developers help page.
Once you have some work ready, submit your patches.
Mailing list for Android contributions is: firstname.lastname@example.org, vlc-devel@ is reserved for core project contributions.
You can help improving translations too by joining the transifex vlc project
You can reach us on IRC:
irc.freenode.net: channel #videolan