It is now clear law that a sperm donor is NEVER a "parent", unless the parties agree in writing beforehand; and that a child conceived by ART (sperm, egg donation +/- a surrogate mother) can have up to 5 (or more) legal parents.
BC is the world's leading jurisdiction for these changes.
The definitive article, for those of you wanting to delve deep into the subject, is "Baby Steps II" by Michelle Kinney and Lynda Cassels. Find it here.