Wow, thats a super tidy installation, my own raspberry bows it's head in shame right now where it sits on a shelf half buried in a tangle of cables with the box half open...
All 'parameters' in pellmon are supplied by a 'plugin', of which there are several installed and activated by default. I guess you mean the 'scotte' parameters, they are handled by a plugin called 'ScotteCom'. The names and descriptions for the 'scotte' parameters are all in the file src/Pellmonsrv/plugins/scottecom/descriptions.py in a structure like this:
dataDescriptions = { #name, unit, description
'magazine_content': ('magazine content', 'kg', 'Calculated magazine content'),
'power': ('power', '%', 'Modulated power level'),
'power_kW': ('power kW', 'kW', 'Calculated power level'),
where for every parameter you have
'ID': ('visual name', 'unit', 'longer description text'),
You can edit these (just not the ID, that needs to stay as it is) as you like and then install it as usual then it will be moved into the correct place, or you can edit the installed file directly at /usr/local/lib/Pellmonsrv/plugins/scottecom/descriptions.py (since it is an interpreted language the source files are executable). Of course installing a new version of PellMon will overwrite these changes so you need to keep track of them and redo the changes. (Using the GIT version management system really helps but it can be hard to get started with)
Other parameters comes from other plugins which mostly consists of just a single file called __init__.py, eg the SiloLevel plugin defines a couple of parameters like this in /src/Pellmonsrv/plugins/silolevel/__init__.py:
itemList=[{'name':'silo_reset_level', 'longname':'Silo fill up level',
'type':'R/W', 'unit':'kg' , 'value':'0', 'min':'0', 'max':'50000'},
{'name':'silo_reset_time', 'longname':'Silo fill up time',
'type':'R/W', 'unit':'' , 'value':'01/01/14 12:00', 'min':'0', 'max':'-'},
...
itemDescriptions = {'silo_reset_level': 'Silo fill up to this amount',
'silo_reset_time' : 'dd/mm/yy hh:mm Automatically set when setting fill up level',
...
The html templates for the webpages are in src/Pellmonweb/html, but the texts defined there are mostly some headlines, and I'm about to move most of that to the plugin system also.
Hope this helps, just ask if you need more pointers / help.
...I suppose PellMon should really have some support for language translations by now, I did not give that much thought when I started as there were only one user then...