there's a lot of user visible strings that talk about a "source" in the po file. in some cases you cannot use another expression, yes. but in some cases you could definitely use less techy speech. use common sense or imagine you are a normal non-CS user and adjust.
i will list a few examples here to make myself clear. i will not list all strings containing the string "source", please also feel free to take a look into e-d-s' po.



#: ../plugins/mail-to-task/mail-to-task.c
"Selected source is read only, thus cannot create task there. Select other 
source, please."

i've seen at least three reports from users who don't get what they should do here. milan, why do you say "source" instead of naming it as what it is in the UI, namely a "task list"? :)
what about
"The task list you are about to add a task to is read only, thus you cannot create a task there. Please select another task list."



#: ../calendar/calendar.error.xml.h:64
msgid ""
"You have a read-only calendar source selected. Change to Calendar View and highlight a calendar that can accept appointments."

WTF is the diff between a calendar and calendar source?
...and why is that string that different from the first one?



#: ../plugins/google-account-setup/org-gnome-evolution-google.eplug.xml.h:2
msgid "Google sources"

does the name have to be that generic? does this plugin also cover gmail, gmemos and gwashmycar, or only a google calendar?



#: ../plugins/groupwise-account-setup/org-gnome-gw-account-setup.eplug.xml.h:1
msgid "A plugin to setup groupwise calendar and contacts sources."

would "servers" instead of "sources" work here?



#: ../plugins/select-one-source/org-gnome-select-one-source.eplug.xml.h:2
msgid "Selects a single calendar or task source for viewing."

why not "task list" here? any reason?