If you sit down with another member of the Drupal community in a cafe to hash out something, then you are with... a friend (hardly, you might barely know each other)? a colleague (doesnt that mean that we are working at the same place)? associate? I am afraid that an open source community being such a new thing it needs a new word. Fellow Drupaler -- sure, try to say that to the average Joe and watch the glassy eyes :) And how do you explain to the average border guard that you are traveling to a code sprint...? A GSoC mentor summit? My explanations sound awkward even to myself, it's a small wonder I was allowed in each time...
Seems to fit.
"A person who shares one's interests or activities; a friend or companion."
http://www.answers.com/comrade
Or.. we just add a "-" to drupal to be dru-pal as the "pal" concept is allready part of the name :)
I already started using "colleague" for that: http://www.garfieldtech.com/blog/colleagues
I would go for "colleague", which in de broad sense is defined as "those united in working for a common purpose". Perhaps with an adjective indicating the common purpose. Or use "fellow software developer".