Humble home page for it:
Download: textures2quake v1 (alpha; not tested on another computer ... should run I hope; 15 MB because it includes some Nexuiz textures to do an easy test)
Takes high resolution textures (Quake3 for example) and scales down 50%, sizes to them power of 2 (GLQuake only supports power of 2 textures) and makes 3 sets available:
1. 24-bit color versions
2. Quake paletted versions
3. Half-Life style: 256 color independent palette
Renames all textures to max length 15 because WAD2 and WAD3 only allow 15 characters in a texture name. Stores a log of those renames in a tab delimited file.
Supports using some other palette instead of the Quake palette, like say the X-Men Ravages of Apocalypse palette. Palette must be in JASC-PAL v 0100 format ... the palette format used by Paintshop Pro.
Only supports conversion from a single folder. Copy all the textures to a single folder to do a multifolder conversion. Source included in zip (uses FreeImage library).