Yup, I'm running 9.1 fine (with 9.1 license server) with a regular apprentice license. My HD license is only 9.0 (I double-checked at
license.sidefx.com).
…
License server version: 9.1.124
…
Installed licenses:
LicID Platform Product Ver Avail Expiry
—– ——– ——- — —– ——
b12821f4 Generic Houdini-Master-NonCommercial 9.1 1/1 11-mar-2008
+.+.+.+ rincewind (license known to: rincewind)
fbecc690 Generic Houdini-Master-NonCommercial 9.0 1/1 01-jan-2037
+.+.+.+ rincewind (license known to: rincewind)
4847d752 Generic Render-NonCommercial 9.1 1/1 11-mar-2008
+.+.+.+ rincewind (license known to: rincewind)
646d625e Generic Render-NonCommercial 9.0 1/1 01-jan-2037
+.+.+.+ rincewind (license known to: rincewind)
1856b84d Generic Houdini-Apprentice-HD 9.0 1/1 01-jan-2037
+.+.+.+ rincewind (license known to: rincewind)
(expired licenses removed for brevity)