Error Component Install: Could not copy PHP install file in 1.5.10

From Joomla! Documentation

The "J1.5" namespace is an archived namespace. This page contains information for a Joomla! version which is no longer supported. It exists only as a historical reference, it will not be improved and its content may be incomplete and/or contain broken links.

Due to changes on the file libraries/joomla/installer/adapters/component.php 15217 Custom Install file upgraded on Component installation, some components that have invalid XML manifest files will not install in version 1.5.10

After installation this error will show:

JInstaller::install: File '/xxxx/tmp/install_49ce897371c92/jfusion.install.php' does not exist.
Component Install: Could not copy PHP install file.

The installer can not find the install.php if this file is not in the root of the component or if the file is not defined to be in a folder on the xml file.

e.g the install.php is located in the folder admin and in the xml the install is:
in 1.5.9 the installer could locate the file, in 1.5.10 not anymore.

Workaround to get your component installed for now, change the location in the xml to folder/install.php
e.g if the file is in folder admin

This is an issue with the component XML manifest file. Please contact the developer to report this problem to ensure that they fix their mistake.

The above suggested modification will not work for older versions of Joomla (just tested on an 1.5.4 installation), because on those, the install file is expected to be located in the admin subdir.
Instead, just move the install-script to the toplevel of the zip, remove it's entry in the <files folder="admin"> section of the script and then repack it. The resulting ZIP will install on both Joomla 1.5.10 as well as on versions <= 1.5.9.