The trunk is the current development version. Where did you download you Inkscape installer?
If you have an official 0.91 version, you should see Inkscape 0.91 (for the 32-bit version) or Inkscape 0.91_64bit r13859 (64-bit) when opening the about dialog (Help>About Inkscape). If you see anything else (another revision or just 0.91 r with no number), it's probably a development version.
The trunk is the current development version. Where did you download you Inkscape installer?
If you have an official 0.91 version, you should see Inkscape 0.91 (for the 32-bit version) or Inkscape 0.91_64bit r13859 (64-bit) when opening the about dialog (Help>About Inkscape). If you see anything else (another revision or just 0.91 r with no number), it's probably a development version.