As can be verified using http://archive.org to view old copies of the website, the wiki content was licensed under the "GNU Free Documentation License 1.2." http://www.gnu.org/licenses/old-licenses/fdl-1.2.html (since superceded by v1.3), e.g.

• https://web.archive.org/web/20060613062104/http://biopython.org:80/wiki/Main_Page (oldest)
• https://web.archive.org/web/20160330125201/http://biopython.org:80/wiki/Main_Page (most recent)

We'd need to check with the contributors since the GitHub migration, and then update the new template here which currently says "All rights reserved.":
https://github.com/biopython/biopython.github.io/blob/master/_includes/sidebar.html#L51

Reported by @hlapp by email.