Well snit. The HUD will not work on the 05 Colorado. works on the 16 but not the 05.
Is the OBD in the 05 the OBDI??
The 05 is definitely not OBDI. In the US OBDII was mandatory starting in 1996, but CANBUS was not standardized upon until 07 or 08. Some vehicles used it before then and some did not. To be fair, he does specifically state OBDII CANBUS and there are a few details around the production years on the site.
I have had some dealings with that vendor around some interior insulation for my Corvette, and he always responded promptly. I didn't find any bad reviews or dealings on CorvetteForum when I was searching, so I agree that it's mostly that the site is just poorly done.
2016 GMC Canyon All Terrain - Cyber Gray
2009 Corvette Z06 - Cyber Gray