The online Macmillan dictionary gives two definitions for
Druid:
- a priest in the ancient Celtic religion
- a member of a modern religious group with similar beliefs to the ancient Druids
The second sense is the more recent one, and many dictionaries don't give such a meaning. Logically, you might expect the word to be written without a capital letter for the priest meaning and capitalized for the member of a religion. However it seems that, if anything, the word was more likely to be capitalized in years gone by, when it generally referred to a priest, soothsayer, bard, etc.
In any case, it appears that the word is still written with a capital letter most of the time, so it is likely that some players will not have noticed the word written in all lower case letters. In future it will be treated as a rare word.