SRP is an "Augmented PAKE" which does not require the server to ever see the plaintext password. I'm not aware of any others that are claimed to be patent-free.
Avoiding patents of other protocols seems to have been one of the goals, but then Thomas has patented SRP itself. https://www.google.com/patents/US6539479 which is set to expire in two years minus 15 days (Jul 14, 1998).
2 or maybe 4 years would be reasonable to earn back (some or all of) the investment, and allow others to improve upon and maybe even patent the new invention. As it stands, whole industries are held back due to 20 years for patents.