Hi @fregger65 , sorry for not answering earlier.
Did I get right that you solved the problem already? If not: Place the jar file in the “addons” directory of openHAB. For most installations, this should be
/usr/share/openhab/addons
Regarding prices: Please note that even if the net price drops below zero, it is very unlikely that the gross price ever will. In Germany the base price we have to pay for every kWh is around 20ct, so the net price would really have to drop heavily to make you earn money for consuming electric power. Partly this is caused by the Renewable Energy Contribution of around 6ct per kWh, so the situation in other countries might indeed be different.
One word regarding the planned extensions: Unfortunately I did not yet find the time to work on them and I doubt that this will change in the next days. So I have to ask you to stay patient (or start working on it yourselves 
)