Their self-description
(source)
DORS/CLUC - Dani otvorenih računarskih sustava / Croatian Linux Users' Conference - is the oldest and biggest regional conference that covers free and open source software, open standards, and the Linux operating system. For the last 26 years, DORS/CLUC has brought together many prominent individuals and companies from the free and open source software community.
# of participants last time
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Call for Participation
The deadline for this CfP passed on 09.03.2019.