If you are on Ubuntu, you probably already know this, but you are on a Debian based system. As such, you will want to follow the (deb) instructions on the sbt download page. go to:
http://www.scala-sbt.org/download.htmlSimply hit ctl+alt+t to open terminal, then copy and paste the lines one-by-one. use ctrl+shift+v to paste into terminal. Don't try to copy and paste more than opne line at a time. It may or may not work.
After installing sbt, type sbt into terminal. This will finish up the installation. If you attempt to build Tritoncore without first running sbt to allow it to finish setting itself up, you will probably run into errors.