Hey Huifei,
Well, the latest version for joomla 1.5 is Hotspots 2.0.5 . The main difference with version 3 is that it is not able to load 100k locations.
With version 2.0.5 you'll be fine if you have no more than 500-1000 locations.
With that said - we no longer support joomla 1.5 (only 2.5, 3.0 and later that year 3.5). It is also a very bad idea to run outdated software, but nobody can stop you

. So if you find a bug in 2.0.5 we are not going to issue an update. Update are going to be only in the latest version.
Regards,
Daniel