"Open data is research data that is freely available on the internet permitting any user to download, copy, analyze, re-process, pass to software or use for any other purpose without financial, legal, or technical barriers other than those inseparable from gaining access to the internet itself."
From SPARC, (the Scholarly Publishing and Academic Resources Coalition):
"Open means anyone can freely access, use, modify, and share for any purpose (subject, at most, to requirements that preserve provenance and openness)."
From Open Knowledge International, a global non-profit organisation focused on realising open data’s value to society by helping civil society groups access and use data to take action on social problems:
Kathy Szigeti, liaison librarian (kszigeti at uwaterloo.ca)
Agnes Zientarska-Kayko, liaison & government information librarian (azientar at uwaterloo.ca)